21556984 has 8 divisors (see below), whose sum is σ = 40419360. Its totient is φ = 10778488.

The previous prime is 21556979. The next prime is 21556987. The reversal of 21556984 is 48965512.

It is a tau number, because it is divible by the number of its divisors (8).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21556987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1347304 + ... + 1347319.

It is an arithmetic number, because the mean of its divisors is an integer number (5052420).

Almost surely, 2^21556984 is an apocalyptic number.

It is an amenable number.

21556984 is a deficient number, since it is larger than the sum of its proper divisors (18862376).

21556984 is a wasteful number, since it uses less digits than its factorization.

21556984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2694629 (or 2694625 counting only the distinct ones).

The product of its digits is 86400, while the sum is 40.

The square root of 21556984 is about 4642.9499243477. The cubic root of 21556984 is about 278.3103343931.

The spelling of 21556984 in words is "twenty-one million, five hundred fifty-six thousand, nine hundred eighty-four".