21631225 has 48 divisors (see below), whose sum is σ = 35462016. Its totient is φ = 12672000.

The previous prime is 21631217. The next prime is 21631237. The reversal of 21631225 is 52213612.

It is not a de Polignac number, because 21631225 - 2³ = 21631217 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21631196 and 21631205.

It is a congruent number.

It is an unprimeable number.

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 47 ways as a sum of consecutive naturals, for example, 32395 + ... + 33055.

It is an arithmetic number, because the mean of its divisors is an integer number (738792).

Almost surely, 2^21631225 is an apocalyptic number.

21631225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21631225 is a deficient number, since it is larger than the sum of its proper divisors (13830791).

21631225 is a wasteful number, since it uses less digits than its factorization.

21631225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 706 (or 701 counting only the distinct ones).

The product of its digits is 720, while the sum is 22.

The square root of 21631225 is about 4650.9380774205. The cubic root of 21631225 is about 278.6294631914.

Adding to 21631225 its reverse (52213612), we get a palindrome (73844837).

The spelling of 21631225 in words is "twenty-one million, six hundred thirty-one thousand, two hundred twenty-five".