21865633 has 12 divisors (see below), whose sum is σ = 23025684. Its totient is φ = 20757600.

The previous prime is 21865619. The next prime is 21865639. The reversal of 21865633 is 33656812.

It can be written as a sum of positive squares in 2 ways, for example, as 5121169 + 16744464 = 2263^2 + 4092^2 .

It is not a de Polignac number, because 21865633 - 2⁹ = 21865121 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21865639) 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, 58435 + ... + 58807.

It is an arithmetic number, because the mean of its divisors is an integer number (1918807).

Almost surely, 2^21865633 is an apocalyptic number.

It is an amenable number.

21865633 is a deficient number, since it is larger than the sum of its proper divisors (1160051).

21865633 is an equidigital number, since it uses as much as digits as its factorization.

21865633 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 496 (or 465 counting only the distinct ones).

The product of its digits is 25920, while the sum is 34.

The square root of 21865633 is about 4676.0702518247. The cubic root of 21865633 is about 279.6323107380.

The spelling of 21865633 in words is "twenty-one million, eight hundred sixty-five thousand, six hundred thirty-three".