21666654 has 24 divisors (see below), whose sum is σ = 48564360. Its totient is φ = 6973008.

The previous prime is 21666649. The next prime is 21666677. The reversal of 21666654 is 45666612.

It is a happy number.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 20232 + ... + 21275.

It is an arithmetic number, because the mean of its divisors is an integer number (2023515).

Almost surely, 2^21666654 is an apocalyptic number.

21666654 is an abundant number, since it is smaller than the sum of its proper divisors (26897706).

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

21666654 is a wasteful number, since it uses less digits than its factorization.

21666654 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41544 (or 41541 counting only the distinct ones).

The product of its digits is 51840, while the sum is 36.

The square root of 21666654 is about 4654.7453206379. The cubic root of 21666654 is about 278.7814992523.

The spelling of 21666654 in words is "twenty-one million, six hundred sixty-six thousand, six hundred fifty-four".