21312388 has 12 divisors (see below), whose sum is σ = 37504012. Its totient is φ = 10596960.

The previous prime is 21312341. The next prime is 21312427. The reversal of 21312388 is 88321312.

It can be written as a sum of positive squares in 2 ways, for example, as 10036224 + 11276164 = 3168^2 + 3358^2 .

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, 13995 + ... + 15442.

Almost surely, 2^21312388 is an apocalyptic number.

It is an amenable number.

21312388 is a deficient number, since it is larger than the sum of its proper divisors (16191624).

21312388 is a wasteful number, since it uses less digits than its factorization.

21312388 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29622 (or 29620 counting only the distinct ones).

The product of its digits is 2304, while the sum is 28.

The square root of 21312388 is about 4616.5341978588. The cubic root of 21312388 is about 277.2537132499.

The spelling of 21312388 in words is "twenty-one million, three hundred twelve thousand, three hundred eighty-eight".