# Journal of Advances in Applied Mathematics

### Number of Digits in Two Integers and Their Multiplication

Download PDF (252.4 KB) PP. 69 - 74 Pub. Date: April 1, 2019

### Author(s)

**Xingbo WANG**

Department of Mechatronic Engineering, Foshan University, Foshan, China Guangdong Engineering Center of Information Security for Intelligent Manufacturing System, Foshan, China State Key Laboratory of Mathematical Engineering and Advanced Computing, Wuxi, China

### Abstract

This paper first proves a formula that discloses the relationship between the number of
digits in multiplication and its two divisors, then proves that the two divisors are of the equal length
if the divisor-ratio generated from the bigger divisor divided by the small one is smaller than 10.
Hence the paper shows that, all the RSA numbers must have two divisors of the equal length.

### Keywords

Number of digits, multiplication, divisor, RSA number.

### References

[1] wikipedia. RSA number, https://en.wikipedia.org/wiki/RSA_numbers

[2] K H Rosen. Elementary Number Theory & Its Application (6th eds), Addison-Wesley ,2010, pp.66

[3] X WANG. “Brief Summary of Frequently-Used Properties of the Floor Function,” IOSR Journal of Mathematics, vol. 13, no. 5, pp. 46 – 48, 2017.

[4] X WANG, “Some New Inequalities With Proofs and Comments on Applications,” Journal of Mathematics Research, vol. 11, no. 3, pp. 15-19, 2018

[5] National Institute of Standards and Technology (NIST). Digital signature standard (DSS), FIPS publication 186-3, June 2009.