20697837521 has 4 divisors (see below), whose sum is σ = 20698645044. Its totient is φ = 20697030000.

The previous prime is 20697837509. The next prime is 20697837529. The reversal of 20697837521 is 12573879602.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7518797521 + 13179040000 = 86711^2 + 114800^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20697837521 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20697837521.

It is not an unprimeable number, because it can be changed into a prime (20697837529) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 364010 + ... + 417011.

It is an arithmetic number, because the mean of its divisors is an integer number (5174661261).

Almost surely, 2^20697837521 is an apocalyptic number.

It is an amenable number.

20697837521 is a deficient number, since it is larger than the sum of its proper divisors (807523).

20697837521 is an equidigital number, since it uses as much as digits as its factorization.

20697837521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 807522.

The product of its (nonzero) digits is 1270080, while the sum is 50.

The spelling of 20697837521 in words is "twenty billion, six hundred ninety-seven million, eight hundred thirty-seven thousand, five hundred twenty-one".