21238816 has 12 divisors (see below), whose sum is σ = 41813982. Its totient is φ = 10619392.

The previous prime is 21238757. The next prime is 21238843. The reversal of 21238816 is 61883212.

It can be written as a sum of positive squares in only one way, i.e., 21123216 + 115600 = 4596^2 + 340^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 331825 + ... + 331888.

Almost surely, 2^21238816 is an apocalyptic number.

It is an amenable number.

21238816 is a deficient number, since it is larger than the sum of its proper divisors (20575166).

21238816 is an equidigital number, since it uses as much as digits as its factorization.

21238816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 663723 (or 663715 counting only the distinct ones).

The product of its digits is 4608, while the sum is 31.

The square root of 21238816 is about 4608.5589938722. The cubic root of 21238816 is about 276.9343117316.

The spelling of 21238816 in words is "twenty-one million, two hundred thirty-eight thousand, eight hundred sixteen".