21633021 has 16 divisors (see below), whose sum is σ = 32155200. Its totient is φ = 14374224.

The previous prime is 21633011. The next prime is 21633023. The reversal of 21633021 is 12033612.

It is not a de Polignac number, because 21633021 - 2⁹ = 21632509 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21632985 and 21633003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21633023) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8215 + ... + 10523.

It is an arithmetic number, because the mean of its divisors is an integer number (2009700).

Almost surely, 2^21633021 is an apocalyptic number.

It is an amenable number.

21633021 is a deficient number, since it is larger than the sum of its proper divisors (10522179).

21633021 is a wasteful number, since it uses less digits than its factorization.

21633021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2665 (or 2659 counting only the distinct ones).

The product of its (nonzero) digits is 216, while the sum is 18.

The square root of 21633021 is about 4651.1311527412. The cubic root of 21633021 is about 278.6371743384.

Adding to 21633021 its reverse (12033612), we get a palindrome (33666633).

It can be divided in two parts, 2163 and 3021, that added together give a square (5184 = 72²).

The spelling of 21633021 in words is "twenty-one million, six hundred thirty-three thousand, twenty-one".