21525431021 has 8 divisors (see below), whose sum is σ = 21571237440. Its totient is φ = 21479655168.

The previous prime is 21525430987. The next prime is 21525431111. The reversal of 21525431021 is 12013452512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21525431021 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21525431621) 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, 1874720 + ... + 1886166.

It is an arithmetic number, because the mean of its divisors is an integer number (2696404680).

Almost surely, 2^21525431021 is an apocalyptic number.

It is an amenable number.

21525431021 is a deficient number, since it is larger than the sum of its proper divisors (45806419).

21525431021 is a wasteful number, since it uses less digits than its factorization.

21525431021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15283.

The product of its (nonzero) digits is 2400, while the sum is 26.

Adding to 21525431021 its reverse (12013452512), we get a palindrome (33538883533).

The spelling of 21525431021 in words is "twenty-one billion, five hundred twenty-five million, four hundred thirty-one thousand, twenty-one".