21002864 has 20 divisors (see below), whose sum is σ = 42463056. Its totient is φ = 10044672.

The previous prime is 21002857. The next prime is 21002881. The reversal of 21002864 is 46820012.

It is a super-2 number, since 2×21002864² = 882240592404992, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 28169 + ... + 28904.

Almost surely, 2^21002864 is an apocalyptic number.

It is an amenable number.

21002864 is an abundant number, since it is smaller than the sum of its proper divisors (21460192).

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

21002864 is a wasteful number, since it uses less digits than its factorization.

21002864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57104 (or 57098 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 23.

The square root of 21002864 is about 4582.8881723210. Note that the first 3 decimals coincide. The cubic root of 21002864 is about 275.9049592249.

Adding to 21002864 its reverse (46820012), we get a palindrome (67822876).

The spelling of 21002864 in words is "twenty-one million, two thousand, eight hundred sixty-four".