21766564 has 6 divisors (see below), whose sum is σ = 38091494. Its totient is φ = 10883280.

The previous prime is 21766553. The next prime is 21766573. The reversal of 21766564 is 46566712.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 21233664 + 532900 = 4608^2 + 730^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2720817 + ... + 2720824.

Almost surely, 2^21766564 is an apocalyptic number.

It is an amenable number.

21766564 is a deficient number, since it is larger than the sum of its proper divisors (16324930).

21766564 is a wasteful number, since it uses less digits than its factorization.

21766564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5441645 (or 5441643 counting only the distinct ones).

The product of its digits is 60480, while the sum is 37.

The square root of 21766564 is about 4665.4650357708. The cubic root of 21766564 is about 279.2093511426.

The spelling of 21766564 in words is "twenty-one million, seven hundred sixty-six thousand, five hundred sixty-four".