21666600 has 72 divisors (see below), whose sum is σ = 72769710. Its totient is φ = 5777280.

The previous prime is 21666587. The next prime is 21666611. The reversal of 21666600 is 666612.

It can be written as a sum of positive squares in 3 ways, for example, as 8749764 + 12916836 = 2958^2 + 3594^2 .

It is a tau number, because it is divible by the number of its divisors (72).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 4219 + ... + 7818.

Almost surely, 2^21666600 is an apocalyptic number.

21666600 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21666600 is an abundant number, since it is smaller than the sum of its proper divisors (51103110).

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

21666600 is a wasteful number, since it uses less digits than its factorization.

21666600 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12059 (or 12047 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 27.

The square root of 21666600 is about 4654.7395201021. The cubic root of 21666600 is about 278.7812676489.

The spelling of 21666600 in words is "twenty-one million, six hundred sixty-six thousand, six hundred".