21990988 has 12 divisors (see below), whose sum is σ = 39115552. Its totient is φ = 10815120.

The previous prime is 21990977. The next prime is 21990989. The reversal of 21990988 is 88909912.

It is a happy number.

It is a super-2 number, since 2×21990988² = 967207106432288, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21990989) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 44820 + ... + 45307.

Almost surely, 2^21990988 is an apocalyptic number.

It is an amenable number.

21990988 is a deficient number, since it is larger than the sum of its proper divisors (17124564).

21990988 is a wasteful number, since it uses less digits than its factorization.

21990988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90192 (or 90190 counting only the distinct ones).

The product of its (nonzero) digits is 93312, while the sum is 46.

The square root of 21990988 is about 4689.4549789928. The cubic root of 21990988 is about 280.1656672666.

The spelling of 21990988 in words is "twenty-one million, nine hundred ninety thousand, nine hundred eighty-eight".