21643974 has 24 divisors (see below), whose sum is σ = 51158952. Its totient is φ = 6558720.

The previous prime is 21643967. The next prime is 21644003. The reversal of 21643974 is 47934612.

21643974 is a `hidden beast` number, since 2 + 1 + 643 + 9 + 7 + 4 = 666.

It is a super-2 number, since 2×21643974² = 936923221025352, which contains 22 as substring.

It is a Curzon number.

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, 54459 + ... + 54854.

It is an arithmetic number, because the mean of its divisors is an integer number (2131623).

Almost surely, 2^21643974 is an apocalyptic number.

21643974 is an abundant number, since it is smaller than the sum of its proper divisors (29514978).

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

21643974 is a wasteful number, since it uses less digits than its factorization.

21643974 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 109332 (or 109329 counting only the distinct ones).

The product of its digits is 36288, while the sum is 36.

The square root of 21643974 is about 4652.3084592490. The cubic root of 21643974 is about 278.6841919362.

The spelling of 21643974 in words is "twenty-one million, six hundred forty-three thousand, nine hundred seventy-four".