21409988 has 12 divisors (see below), whose sum is σ = 37716672. Its totient is φ = 10633800.

The previous prime is 21409931. The next prime is 21409991. The reversal of 21409988 is 88990412.

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, 17120 + ... + 18327.

It is an arithmetic number, because the mean of its divisors is an integer number (3143056).

Almost surely, 2^21409988 is an apocalyptic number.

It is an amenable number.

21409988 is a deficient number, since it is larger than the sum of its proper divisors (16306684).

21409988 is a wasteful number, since it uses less digits than its factorization.

21409988 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35602 (or 35600 counting only the distinct ones).

The product of its (nonzero) digits is 41472, while the sum is 41.

The square root of 21409988 is about 4627.0928237934. The cubic root of 21409988 is about 277.6762962751.

The spelling of 21409988 in words is "twenty-one million, four hundred nine thousand, nine hundred eighty-eight".