21113864 has 32 divisors (see below), whose sum is σ = 44128800. Its totient is φ = 9411840.

The previous prime is 21113861. The next prime is 21113887. The reversal of 21113864 is 46831112.

21113864 = 97² + 98² + ... + 400².

It is not an unprimeable number, because it can be changed into a prime (21113861) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1502 + ... + 6669.

It is an arithmetic number, because the mean of its divisors is an integer number (1379025).

Almost surely, 2^21113864 is an apocalyptic number.

It is an amenable number.

21113864 is an abundant number, since it is smaller than the sum of its proper divisors (23014936).

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

21113864 is a wasteful number, since it uses less digits than its factorization.

21113864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8213 (or 8209 counting only the distinct ones).

The product of its digits is 1152, while the sum is 26.

The square root of 21113864 is about 4594.9824809242. The cubic root of 21113864 is about 276.3901574429.

Adding to 21113864 its reverse (46831112), we get a palindrome (67944976).

The spelling of 21113864 in words is "twenty-one million, one hundred thirteen thousand, eight hundred sixty-four".