21766866 has 16 divisors (see below), whose sum is σ = 47491488. Its totient is φ = 6596000.

The previous prime is 21766853. The next prime is 21766873. The reversal of 21766866 is 66866712.

It is a happy 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, 164835 + ... + 164966.

It is an arithmetic number, because the mean of its divisors is an integer number (2968218).

Almost surely, 2^21766866 is an apocalyptic number.

21766866 is an abundant number, since it is smaller than the sum of its proper divisors (25724622).

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

21766866 is a wasteful number, since it uses less digits than its factorization.

21766866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 329817.

The product of its digits is 145152, while the sum is 42.

The square root of 21766866 is about 4665.4974011353. The cubic root of 21766866 is about 279.2106424325.

The spelling of 21766866 in words is "twenty-one million, seven hundred sixty-six thousand, eight hundred sixty-six".