21766816 has 12 divisors (see below), whose sum is σ = 42853482. Its totient is φ = 10883392.

The previous prime is 21766757. The next prime is 21766831. The reversal of 21766816 is 61866712.

It can be written as a sum of positive squares in only one way, i.e., 19395216 + 2371600 = 4404^2 + 1540^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 340075 + ... + 340138.

Almost surely, 2^21766816 is an apocalyptic number.

It is an amenable number.

21766816 is a deficient number, since it is larger than the sum of its proper divisors (21086666).

21766816 is an equidigital number, since it uses as much as digits as its factorization.

21766816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 680223 (or 680215 counting only the distinct ones).

The product of its digits is 24192, while the sum is 37.

The square root of 21766816 is about 4665.4920426467. The cubic root of 21766816 is about 279.2104286436.

The spelling of 21766816 in words is "twenty-one million, seven hundred sixty-six thousand, eight hundred sixteen".