21397212 has 18 divisors (see below), whose sum is σ = 54087488. Its totient is φ = 7132392.

The previous prime is 21397171. The next prime is 21397217. The reversal of 21397212 is 21279312.

It is a tau number, because it is divible by the number of its divisors (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21397217) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 297148 + ... + 297219.

Almost surely, 2^21397212 is an apocalyptic number.

It is an amenable number.

21397212 is an abundant number, since it is smaller than the sum of its proper divisors (32690276).

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

21397212 is a wasteful number, since it uses less digits than its factorization.

21397212 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 594377 (or 594372 counting only the distinct ones).

The product of its digits is 1512, while the sum is 27.

The square root of 21397212 is about 4625.7120532951. The cubic root of 21397212 is about 277.6210526158.

It can be divided in two parts, 21397 and 212, that added together give a square (21609 = 147²).

The spelling of 21397212 in words is "twenty-one million, three hundred ninety-seven thousand, two hundred twelve".