21636666 has 16 divisors (see below), whose sum is σ = 48081600. Its totient is φ = 7212204.

The previous prime is 21636661. The next prime is 21636677. The reversal of 21636666 is 66663612.

It is a nude number because it is divisible by every one of its digits.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21636666.

It is not an unprimeable number, because it can be changed into a prime (21636661) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 200286 + ... + 200393.

It is an arithmetic number, because the mean of its divisors is an integer number (3005100).

Almost surely, 2^21636666 is an apocalyptic number.

21636666 is an abundant number, since it is smaller than the sum of its proper divisors (26444934).

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

21636666 is a wasteful number, since it uses less digits than its factorization.

21636666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 400690 (or 400684 counting only the distinct ones).

The product of its digits is 46656, while the sum is 36.

The square root of 21636666 is about 4651.5229764025. The cubic root of 21636666 is about 278.6528228765.

The spelling of 21636666 in words is "twenty-one million, six hundred thirty-six thousand, six hundred sixty-six".