21531712 has 28 divisors (see below), whose sum is σ = 44978320. Its totient is φ = 10198656.

The previous prime is 21531709. The next prime is 21531721. The reversal of 21531712 is 21713512.

It is a happy number.

It is a super-2 number, since 2×21531712² = 927229243301888, which contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7638 + ... + 10069.

Almost surely, 2^21531712 is an apocalyptic number.

It is an amenable number.

21531712 is an abundant number, since it is smaller than the sum of its proper divisors (23446608).

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

21531712 is a wasteful number, since it uses less digits than its factorization.

21531712 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17738 (or 17728 counting only the distinct ones).

The product of its digits is 420, while the sum is 22.

The square root of 21531712 is about 4640.2275806258. The cubic root of 21531712 is about 278.2015342461.

The spelling of 21531712 in words is "twenty-one million, five hundred thirty-one thousand, seven hundred twelve".