21031212 has 12 divisors (see below), whose sum is σ = 49072856. Its totient is φ = 7010400.

The previous prime is 21031187. The next prime is 21031217. The reversal of 21031212 is 21213012.

It is a tau number, because it is divible by the number of its divisors (12).

It is a Harshad number since it is a multiple of its sum of digits (12), and also a Moran number because the ratio is a prime number: 1752601 = 21031212 / (2 + 1 + 0 + 3 + 1 + 2 + 1 + 2).

It is not an unprimeable number, because it can be changed into a prime (21031217) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 876289 + ... + 876312.

Almost surely, 2^21031212 is an apocalyptic number.

It is an amenable number.

21031212 is an abundant number, since it is smaller than the sum of its proper divisors (28041644).

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

21031212 is a wasteful number, since it uses less digits than its factorization.

21031212 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1752608 (or 1752606 counting only the distinct ones).

The product of its (nonzero) digits is 24, while the sum is 12.

The square root of 21031212 is about 4585.9799389007. The cubic root of 21031212 is about 276.0290349627.

Adding to 21031212 its reverse (21213012), we get a palindrome (42244224).

The spelling of 21031212 in words is "twenty-one million, thirty-one thousand, two hundred twelve".