21255312 has 80 divisors (see below), whose sum is σ = 61746048. Its totient is φ = 6251520.

The previous prime is 21255307. The next prime is 21255317. The reversal of 21255312 is 21355212.

It is an interprime number because it is at equal distance from previous prime (21255307) and next prime (21255317).

It is not an unprimeable number, because it can be changed into a prime (21255317) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13612 + ... + 15092.

Almost surely, 2^21255312 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21255312, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30873024).

21255312 is an abundant number, since it is smaller than the sum of its proper divisors (40490736).

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

21255312 is a wasteful number, since it uses less digits than its factorization.

21255312 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1528 (or 1522 counting only the distinct ones).

The product of its digits is 600, while the sum is 21.

The square root of 21255312 is about 4610.3483599398. The cubic root of 21255312 is about 277.0059906518.

The spelling of 21255312 in words is "twenty-one million, two hundred fifty-five thousand, three hundred twelve".