21945636 has 18 divisors (see below), whose sum is σ = 55473782. Its totient is φ = 7315200.

The previous prime is 21945601. The next prime is 21945641. The reversal of 21945636 is 63654912.

It is a happy number.

21945636 is a `hidden beast` number, since 2 + 1 + 94 + 563 + 6 = 666.

It can be written as a sum of positive squares in only one way, i.e., 19713600 + 2232036 = 4440^2 + 1494^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a super-2 number, since 2×21945636² = 963221878888992, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 609601 = 21945636 / (2 + 1 + 9 + 4 + 5 + 6 + 3 + 6).

It is a self number, because there is not a number n which added to its sum of digits gives 21945636.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 304765 + ... + 304836.

Almost surely, 2^21945636 is an apocalyptic number.

It is an amenable number.

21945636 is an abundant number, since it is smaller than the sum of its proper divisors (33528146).

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

21945636 is a wasteful number, since it uses less digits than its factorization.

21945636 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 609611 (or 609606 counting only the distinct ones).

The product of its digits is 38880, while the sum is 36.

The square root of 21945636 is about 4684.6169533912. The cubic root of 21945636 is about 279.9729395617.

The spelling of 21945636 in words is "twenty-one million, nine hundred forty-five thousand, six hundred thirty-six".