21186645 has 16 divisors (see below), whose sum is σ = 33962112. Its totient is φ = 11278400.

The previous prime is 21186637. The next prime is 21186677. The reversal of 21186645 is 54668112.

It is not a de Polignac number, because 21186645 - 2³ = 21186637 is a prime.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10195 + ... + 12095.

It is an arithmetic number, because the mean of its divisors is an integer number (2122632).

Almost surely, 2^21186645 is an apocalyptic number.

It is an amenable number.

21186645 is a deficient number, since it is larger than the sum of its proper divisors (12775467).

21186645 is a wasteful number, since it uses less digits than its factorization.

21186645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2652.

The product of its digits is 11520, while the sum is 33.

The square root of 21186645 is about 4602.8952844921. The cubic root of 21186645 is about 276.7073721176.

The spelling of 21186645 in words is "twenty-one million, one hundred eighty-six thousand, six hundred forty-five".