21247212 has 48 divisors (see below), whose sum is σ = 59996160. Its totient is φ = 5713152.

The previous prime is 21247211. The next prime is 21247231. The reversal of 21247212 is 21274212.

It is a Harshad number since it is a multiple of its sum of digits (21).

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 (21247211) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 6012 + ... + 8867.

It is an arithmetic number, because the mean of its divisors is an integer number (1249920).

Almost surely, 2^21247212 is an apocalyptic number.

It is an amenable number.

21247212 is an abundant number, since it is smaller than the sum of its proper divisors (38748948).

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

21247212 is a wasteful number, since it uses less digits than its factorization.

21247212 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14910 (or 14908 counting only the distinct ones).

The product of its digits is 448, while the sum is 21.

The square root of 21247212 is about 4609.4698176688. The cubic root of 21247212 is about 276.9707989219.

Subtracting 21247212 from its reverse (21274212), we obtain a cube (27000 = 30³).

The spelling of 21247212 in words is "twenty-one million, two hundred forty-seven thousand, two hundred twelve".