21291312 has 40 divisors (see below), whose sum is σ = 62861056. Its totient is φ = 6083136.

The previous prime is 21291311. The next prime is 21291337. The reversal of 21291312 is 21319212.

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

It is not an unprimeable number, because it can be changed into a prime (21291311) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 31348 + ... + 32019.

Almost surely, 2^21291312 is an apocalyptic number.

It is an amenable number.

21291312 is an abundant number, since it is smaller than the sum of its proper divisors (41569744).

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

21291312 is a wasteful number, since it uses less digits than its factorization.

21291312 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 63385 (or 63379 counting only the distinct ones).

The product of its digits is 216, while the sum is 21.

The square root of 21291312 is about 4614.2509684671. The cubic root of 21291312 is about 277.1622902629.

The spelling of 21291312 in words is "twenty-one million, two hundred ninety-one thousand, three hundred twelve".