21645364 has 12 divisors (see below), whose sum is σ = 40793284. Its totient is φ = 9990144.

The previous prime is 21645343. The next prime is 21645373. The reversal of 21645364 is 46354612.

It can be written as a sum of positive squares in 2 ways, for example, as 13749264 + 7896100 = 3708^2 + 2810^2 .

It is a hoax number, since the sum of its digits (31) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 208077 + ... + 208180.

Almost surely, 2^21645364 is an apocalyptic number.

It is an amenable number.

21645364 is a deficient number, since it is larger than the sum of its proper divisors (19147920).

21645364 is a wasteful number, since it uses less digits than its factorization.

21645364 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 416274 (or 416272 counting only the distinct ones).

The product of its digits is 17280, while the sum is 31.

The square root of 21645364 is about 4652.4578450535. The cubic root of 21645364 is about 278.6901576111.

Adding to 21645364 its reverse (46354612), we get a palindrome (67999976).

The spelling of 21645364 in words is "twenty-one million, six hundred forty-five thousand, three hundred sixty-four".