21621388 has 12 divisors (see below), whose sum is σ = 38089072. Its totient is φ = 10738800.

The previous prime is 21621377. The next prime is 21621401. The reversal of 21621388 is 88312612.

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, 17295 + ... + 18502.

Almost surely, 2^21621388 is an apocalyptic number.

It is an amenable number.

21621388 is a deficient number, since it is larger than the sum of its proper divisors (16467684).

21621388 is a wasteful number, since it uses less digits than its factorization.

21621388 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35952 (or 35950 counting only the distinct ones).

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

The square root of 21621388 is about 4649.8804285702. The cubic root of 21621388 is about 278.5872203439.

The spelling of 21621388 in words is "twenty-one million, six hundred twenty-one thousand, three hundred eighty-eight".