21633631 has 4 divisors (see below), whose sum is σ = 21650200. Its totient is φ = 21617064.

The previous prime is 21633617. The next prime is 21633637. The reversal of 21633631 is 13633612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21633631 - 2⁹ = 21633119 is a prime.

It is a super-3 number, since 3×21633631³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21633596 and 21633605.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21633637) 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 3 ways as a sum of consecutive naturals, for example, 6141 + ... + 8998.

It is an arithmetic number, because the mean of its divisors is an integer number (5412550).

Almost surely, 2^21633631 is an apocalyptic number.

21633631 is a deficient number, since it is larger than the sum of its proper divisors (16569).

21633631 is a wasteful number, since it uses less digits than its factorization.

21633631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16568.

The product of its digits is 1944, while the sum is 25.

The square root of 21633631 is about 4651.1967277250. The cubic root of 21633631 is about 278.6397932834.

The spelling of 21633631 in words is "twenty-one million, six hundred thirty-three thousand, six hundred thirty-one".