21151864 has 32 divisors (see below), whose sum is σ = 42886800. Its totient is φ = 9745920.

The previous prime is 21151813. The next prime is 21151873. The reversal of 21151864 is 46815112.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3744 + ... + 7504.

Almost surely, 2^21151864 is an apocalyptic number.

It is an amenable number.

21151864 is an abundant number, since it is smaller than the sum of its proper divisors (21734936).

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

21151864 is a wasteful number, since it uses less digits than its factorization.

21151864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3823 (or 3819 counting only the distinct ones).

The product of its digits is 1920, while the sum is 28.

The square root of 21151864 is about 4599.1155671498. The cubic root of 21151864 is about 276.5558705402. Note that the first 3 decimals are identical.

Adding to 21151864 its reverse (46815112), we get a palindrome (67966976).

The spelling of 21151864 in words is "twenty-one million, one hundred fifty-one thousand, eight hundred sixty-four".