21556644 has 48 divisors (see below), whose sum is σ = 52808448. Its totient is φ = 6835968.

The previous prime is 21556643. The next prime is 21556649. The reversal of 21556644 is 44665512.

It is a hoax number, since the sum of its digits (33) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21556643) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 20352 + ... + 21384.

It is an arithmetic number, because the mean of its divisors is an integer number (1100176).

Almost surely, 2^21556644 is an apocalyptic number.

It is an amenable number.

21556644 is an abundant number, since it is smaller than the sum of its proper divisors (31251804).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21556644 is a wasteful number, since it uses less digits than its factorization.

21556644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1124 (or 1122 counting only the distinct ones).

The product of its digits is 28800, while the sum is 33.

The square root of 21556644 is about 4642.9133095504. The cubic root of 21556644 is about 278.3088712012.

The spelling of 21556644 in words is "twenty-one million, five hundred fifty-six thousand, six hundred forty-four".