21605652 has 36 divisors (see below), whose sum is σ = 54794740. Its totient is φ = 7178112.

The previous prime is 21605627. The next prime is 21605659. The reversal of 21605652 is 25650612.

21605652 is a `hidden beast` number, since 2 + 1 + 6 + 0 + 5 + 652 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 17589636 + 4016016 = 4194^2 + 2004^2 .

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21605659) 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 11 ways as a sum of consecutive naturals, for example, 12624 + ... + 14232.

Almost surely, 2^21605652 is an apocalyptic number.

It is an amenable number.

21605652 is an abundant number, since it is smaller than the sum of its proper divisors (33189088).

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

21605652 is a wasteful number, since it uses less digits than its factorization.

21605652 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1992 (or 1987 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 27.

The square root of 21605652 is about 4648.1880340623. The cubic root of 21605652 is about 278.5196188799.

The spelling of 21605652 in words is "twenty-one million, six hundred five thousand, six hundred fifty-two".