21667990 has 16 divisors (see below), whose sum is σ = 39739248. Its totient is φ = 8503456.

The previous prime is 21667973. The next prime is 21668011. The reversal of 21667990 is 9976612.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19912 + ... + 20971.

It is an arithmetic number, because the mean of its divisors is an integer number (2483703).

Almost surely, 2^21667990 is an apocalyptic number.

21667990 is a deficient number, since it is larger than the sum of its proper divisors (18071258).

21667990 is a wasteful number, since it uses less digits than its factorization.

21667990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40943.

The product of its (nonzero) digits is 40824, while the sum is 40.

The square root of 21667990 is about 4654.8888278884. Note that the first 4 decimals coincide. The cubic root of 21667990 is about 278.7872291699.

The spelling of 21667990 in words is "twenty-one million, six hundred sixty-seven thousand, nine hundred ninety".