21004864 has 28 divisors (see below), whose sum is σ = 42574464. Its totient is φ = 10277504.

The previous prime is 21004847. The next prime is 21004883. The reversal of 21004864 is 46840012.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 484 + ... + 6499.

Almost surely, 2^21004864 is an apocalyptic number.

It is an amenable number.

21004864 is an abundant number, since it is smaller than the sum of its proper divisors (21569600).

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

21004864 is an equidigital number, since it uses as much as digits as its factorization.

21004864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7042 (or 7032 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 25.

The square root of 21004864 is about 4583.1063701381. The cubic root of 21004864 is about 275.9137166401.

Adding to 21004864 its reverse (46840012), we get a palindrome (67844876).

The spelling of 21004864 in words is "twenty-one million, four thousand, eight hundred sixty-four".