21905666 has 16 divisors (see below), whose sum is σ = 33699456. Its totient is φ = 10674576.

The previous prime is 21905647. The next prime is 21905687. The reversal of 21905666 is 66650912.

It is a happy number.

It is a Curzon 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, 37025 + ... + 37611.

It is an arithmetic number, because the mean of its divisors is an integer number (2106216).

Almost surely, 2^21905666 is an apocalyptic number.

21905666 is a deficient number, since it is larger than the sum of its proper divisors (11793790).

21905666 is a wasteful number, since it uses less digits than its factorization.

21905666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1033.

The product of its (nonzero) digits is 19440, while the sum is 35.

The square root of 21905666 is about 4680.3489186171. The cubic root of 21905666 is about 279.8028629367.

The spelling of 21905666 in words is "twenty-one million, nine hundred five thousand, six hundred sixty-six".