Addition

Multiplication

Multiplication

Square Roots

Calendar

Mental Calculation: Division

Mental Calculation: Factorizing Numbers

Other Remarkable Achievements

• Finding consecutive primes: Consecutive primes are prime numbers for which no other prime number between them exist. An example of five consecutive primes is the sequence 4001, 4003, 4007, 4013 and 4019. From the product of four consecutive primes, Willem Bouman (Netherlands) is able to calculate the primes that have been multiplied. In a record attempt on 12 may 2012 in Alphen an der Rijn, he needed an average time of 7:26 minutes for 13-digit products, an average time of 6:06 minutes for 14-digit products, an average time of 13:21 minutes for 15-digit products and an average time of 23:24 minutes for 16-digit products. For each category, he correctly solved three problems.
  
• Flash Anzan: 15 three-digit numbers (from 100-999) flash up on a screen, and the sum of those numbers has to be calculated. At the All Japan Soroban Championship on 8 August 2012 in Kyoto, Takeo Sasano (Japan) set a record in this category when the numbers were flashed in only 1.70 seconds. This video shows his previous record of 1.80 seconds.
  Granth Rakesh Thakkar (India) was able to add 150 one-digit numbers flashing up on a screen at a period of 0.3 seconds on 5 September 2013 at Memoriad Center in Ankara, Turkey. For being accepted as a record, he had to solve a sequence of five such tasks in a row without an error.
  Ömer Yiğit Ağma (Turkey) was able to add 150 one-digit numbers flashing up on a screen at a period of 0.2 seconds on 29 November 2015 at Memoriad World Record Attempts Week, Beylikduzu, Istanbul. For being accepted as a record, he had to solve a sequence of five such tasks in a row without an error.
  The fastest time to add 50 five-digit numbers (the time needed to type in the answer was included into the measurement) were 25.19 seconds by Aaryan Shukla (India) on 29 February 2024 in the TV show "Lo Show die Record" in Milan, Italy. VIDEO
  
• Multiplying 20-digit numbers:  Aaryan Shukla (India) multiplied two 20-digit numbers correctly in 1:45 minutes on 17 July 2022 at the Mental Calculation World Cup in Paderborn (Germany)
  Previous records:
  Granth Rakesh Thakkar (India) 2:48 minutes on 12 October 2014 at Days Inn Hotel in Dresden (Germany)
  Granth Rakesh Thakkar (India) 4:44 minutes on 2 September 2013 at Memoriad Center in Ankara (Turkey) VIDEO
  Halil Uğur Adıgüzel (Turkey) 4:30 minutes on 15 March 2014 at Demora Hotel in Ankara at the Brain Awareness Week 2014
  Shourya Maheshwari (India) 3:59 minutes on 12 October 2014 at Days Inn Hotel in Dresden (Germany)
• Sum of 4 Squares: Kaloyan Geshev (Bulgaria) correctly wrote ten 5-digit numbers as the sum of at most four squares in 1:14.2 minutes on 16 December 2024 at the New Bulgarian University in Sofia
  Previous record:
  Willem Bouman (Netherlands) 4:54.6 Minutes on 10 February 2020 at the Eidhoven Universtiy of Technology.

• Calculations on Paper - cubic roots: Willem Bouman (Netherlands) correctly calculated the cube root of an odd integer of 36 digits (which was a perfect cube) in 8:44 minutes on 21 May 2022 at the Eidhoven Universtiy of Technology.