21610666 has 24 divisors (see below), whose sum is σ = 41138496. Its totient is φ = 8419320.

The previous prime is 21610661. The next prime is 21610669. The reversal of 21610666 is 66601612.

It is not an unprimeable number, because it can be changed into a prime (21610661) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 8946 + ... + 11101.

It is an arithmetic number, because the mean of its divisors is an integer number (1714104).

Almost surely, 2^21610666 is an apocalyptic number.

21610666 is a deficient number, since it is larger than the sum of its proper divisors (19527830).

21610666 is a wasteful number, since it uses less digits than its factorization.

21610666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20074 (or 20067 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 28.

The square root of 21610666 is about 4648.7273527278. The cubic root of 21610666 is about 278.5411624611.

The spelling of 21610666 in words is "twenty-one million, six hundred ten thousand, six hundred sixty-six".