21631212 has 30 divisors (see below), whose sum is σ = 56549108. Its totient is φ = 7210296.

The previous prime is 21631171. The next prime is 21631213. The reversal of 21631212 is 21213612.

21631212 is a `hidden beast` number, since 21 + 631 + 2 + 12 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (21631213) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 33058 + ... + 33705.

Almost surely, 2^21631212 is an apocalyptic number.

It is an amenable number.

21631212 is an abundant number, since it is smaller than the sum of its proper divisors (34917896).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21631212 is a wasteful number, since it uses less digits than its factorization.

21631212 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66779 (or 66768 counting only the distinct ones).

The product of its digits is 144, while the sum is 18.

The square root of 21631212 is about 4650.9366798528. The cubic root of 21631212 is about 278.6294073742.

Adding to 21631212 its reverse (21213612), we get a palindrome (42844824).

It can be divided in two parts, 2163 and 1212, that added together give a cube (3375 = 15³).

The spelling of 21631212 in words is "twenty-one million, six hundred thirty-one thousand, two hundred twelve".