21666986 has 12 divisors (see below), whose sum is σ = 35724066. Its totient is φ = 9848520.

The previous prime is 21666979. The next prime is 21666991. The reversal of 21666986 is 68966612.

It can be written as a sum of positive squares in only one way, i.e., 12780625 + 8886361 = 3575^2 + 2981^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 44525 + ... + 45008.

Almost surely, 2^21666986 is an apocalyptic number.

21666986 is a deficient number, since it is larger than the sum of its proper divisors (14057080).

21666986 is a wasteful number, since it uses less digits than its factorization.

21666986 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 89557 (or 89546 counting only the distinct ones).

The product of its digits is 186624, while the sum is 44.

The square root of 21666986 is about 4654.7809830324. The cubic root of 21666986 is about 278.7829231760.

The spelling of 21666986 in words is "twenty-one million, six hundred sixty-six thousand, nine hundred eighty-six".