21642988 has 6 divisors (see below), whose sum is σ = 37875236. Its totient is φ = 10821492.

The previous prime is 21642979. The next prime is 21643009. The reversal of 21642988 is 88924612.

It is a self number, because there is not a number n which added to its sum of digits gives 21642988.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2705370 + ... + 2705377.

Almost surely, 2^21642988 is an apocalyptic number.

It is an amenable number.

21642988 is a deficient number, since it is larger than the sum of its proper divisors (16232248).

21642988 is a wasteful number, since it uses less digits than its factorization.

21642988 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5410751 (or 5410749 counting only the distinct ones).

The product of its digits is 55296, while the sum is 40.

The square root of 21642988 is about 4652.2024891443. The cubic root of 21642988 is about 278.6799600149.

The spelling of 21642988 in words is "twenty-one million, six hundred forty-two thousand, nine hundred eighty-eight".