21666984 has 64 divisors (see below), whose sum is σ = 55944000. Its totient is φ = 6990336.

The previous prime is 21666979. The next prime is 21666991. The reversal of 21666984 is 48966612.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 145342 + ... + 145490.

It is an arithmetic number, because the mean of its divisors is an integer number (874125).

Almost surely, 2^21666984 is an apocalyptic number.

21666984 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21666984 is an abundant number, since it is smaller than the sum of its proper divisors (34277016).

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

21666984 is a wasteful number, since it uses less digits than its factorization.

21666984 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 314 (or 310 counting only the distinct ones).

The product of its digits is 124416, while the sum is 42.

The square root of 21666984 is about 4654.7807681995. The cubic root of 21666984 is about 278.7829145982.

The spelling of 21666984 in words is "twenty-one million, six hundred sixty-six thousand, nine hundred eighty-four".