21287402521 has 16 divisors (see below), whose sum is σ = 26554871808. Its totient is φ = 16578378000.

The previous prime is 21287402519. The next prime is 21287402537. The reversal of 21287402521 is 12520478212.

It is a cyclic number.

It is not a de Polignac number, because 21287402521 - 2¹ = 21287402519 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21287402021) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 64546 + ... + 216196.

It is an arithmetic number, because the mean of its divisors is an integer number (1659679488).

Almost surely, 2^21287402521 is an apocalyptic number.

It is an amenable number.

21287402521 is a deficient number, since it is larger than the sum of its proper divisors (5267469287).

21287402521 is a wasteful number, since it uses less digits than its factorization.

21287402521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 153492.

The product of its (nonzero) digits is 17920, while the sum is 34.

The spelling of 21287402521 in words is "twenty-one billion, two hundred eighty-seven million, four hundred two thousand, five hundred twenty-one".