21939966 has 24 divisors (see below), whose sum is σ = 47623680. Its totient is φ = 7299936.

The previous prime is 21939937. The next prime is 21939977. The reversal of 21939966 is 66993912.

It is a happy number.

It is a nude number because it is divisible by every one of its digits.

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, 16515 + ... + 17793.

It is an arithmetic number, because the mean of its divisors is an integer number (1984320).

Almost surely, 2^21939966 is an apocalyptic number.

21939966 is an abundant number, since it is smaller than the sum of its proper divisors (25683714).

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

21939966 is a wasteful number, since it uses less digits than its factorization.

21939966 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2240 (or 2237 counting only the distinct ones).

The product of its digits is 157464, while the sum is 45.

The square root of 21939966 is about 4684.0117420861. The cubic root of 21939966 is about 279.9488256817.

The spelling of 21939966 in words is "twenty-one million, nine hundred thirty-nine thousand, nine hundred sixty-six".