21997172526 has 16 divisors (see below), whose sum is σ = 50279251584. Its totient is φ = 6284906424.

The previous prime is 21997172521. The next prime is 21997172551. The reversal of 21997172526 is 62527179912.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21997172521) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 261871060 + ... + 261871143.

It is an arithmetic number, because the mean of its divisors is an integer number (3142453224).

Almost surely, 2^21997172526 is an apocalyptic number.

21997172526 is an abundant number, since it is smaller than the sum of its proper divisors (28282079058).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21997172526 is a wasteful number, since it uses less digits than its factorization.

21997172526 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 523742215.

The product of its digits is 952560, while the sum is 51.

The spelling of 21997172526 in words is "twenty-one billion, nine hundred ninety-seven million, one hundred seventy-two thousand, five hundred twenty-six".