21989564 has 12 divisors (see below), whose sum is σ = 40155024. Its totient is φ = 10516704.

The previous prime is 21989557. The next prime is 21989579. The reversal of 21989564 is 46598912.

21989564 = T₃₉₄ + T₃₉₅ + ... + T₅₇₇.

It is a congruent number.

It is an unprimeable number.

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, 119417 + ... + 119600.

It is an arithmetic number, because the mean of its divisors is an integer number (3346252).

Almost surely, 2^21989564 is an apocalyptic number.

It is an amenable number.

21989564 is a deficient number, since it is larger than the sum of its proper divisors (18165460).

21989564 is a wasteful number, since it uses less digits than its factorization.

21989564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 239044 (or 239042 counting only the distinct ones).

The product of its digits is 155520, while the sum is 44.

The square root of 21989564 is about 4689.3031465240. The cubic root of 21989564 is about 280.1596198724.

The spelling of 21989564 in words is "twenty-one million, nine hundred eighty-nine thousand, five hundred sixty-four".