21517984 has 24 divisors (see below), whose sum is σ = 42657300. Its totient is φ = 10684416.

The previous prime is 21517973. The next prime is 21518009. The reversal of 21517984 is 48971512.

It can be written as a sum of positive squares in 2 ways, for example, as 14653584 + 6864400 = 3828^2 + 2620^2 .

It is a Smith number, since the sum of its digits (37) coincides with the sum of the digits of its prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2512 + ... + 7024.

Almost surely, 2^21517984 is an apocalyptic number.

It is an amenable number.

21517984 is a deficient number, since it is larger than the sum of its proper divisors (21139316).

21517984 is a wasteful number, since it uses less digits than its factorization.

21517984 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4672 (or 4664 counting only the distinct ones).

The product of its digits is 20160, while the sum is 37.

The square root of 21517984 is about 4638.7481069789. The cubic root of 21517984 is about 278.1423972453.

The spelling of 21517984 in words is "twenty-one million, five hundred seventeen thousand, nine hundred eighty-four".