21648636 has 36 divisors (see below), whose sum is σ = 54912312. Its totient is φ = 7191264.

The previous prime is 21648631. The next prime is 21648647. The reversal of 21648636 is 63684612.

21648636 is a `hidden beast` number, since 2 + 1 + 648 + 6 + 3 + 6 = 666.

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21648636.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21648631) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 11626 + ... + 13358.

It is an arithmetic number, because the mean of its divisors is an integer number (1525342).

Almost surely, 2^21648636 is an apocalyptic number.

It is an amenable number.

21648636 is an abundant number, since it is smaller than the sum of its proper divisors (33263676).

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

21648636 is a wasteful number, since it uses less digits than its factorization.

21648636 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2090 (or 2085 counting only the distinct ones).

The product of its digits is 41472, while the sum is 36.

The square root of 21648636 is about 4652.8094738556. The cubic root of 21648636 is about 278.7041995441.

It can be divided in two parts, 21648 and 636, that multiplied together give a triangular number (13768128 = T₅₂₄₇).

The spelling of 21648636 in words is "twenty-one million, six hundred forty-eight thousand, six hundred thirty-six".