21531403256 has 32 divisors (see below), whose sum is σ = 44098916400. Its totient is φ = 9774243840.

The previous prime is 21531403253. The next prime is 21531403259. The reversal of 21531403256 is 65230413512.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21531403253) and next prime (21531403259).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21531403253) 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, 91415 + ... + 226758.

Almost surely, 2^21531403256 is an apocalyptic number.

It is an amenable number.

21531403256 is an abundant number, since it is smaller than the sum of its proper divisors (22567513144).

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

21531403256 is a wasteful number, since it uses less digits than its factorization.

21531403256 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 318959 (or 318955 counting only the distinct ones).

The product of its (nonzero) digits is 21600, while the sum is 32.

Adding to 21531403256 its reverse (65230413512), we get a palindrome (86761816768).

The spelling of 21531403256 in words is "twenty-one billion, five hundred thirty-one million, four hundred three thousand, two hundred fifty-six".