21721512 has 32 divisors (see below), whose sum is σ = 57499200. Its totient is φ = 6814464.

The previous prime is 21721507. The next prime is 21721517. The reversal of 21721512 is 21512712.

It is an interprime number because it is at equal distance from previous prime (21721507) and next prime (21721517).

It is a super-2 number, since 2×21721512² = 943648167132288, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21721517) 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, 26212 + ... + 27027.

It is an arithmetic number, because the mean of its divisors is an integer number (1796850).

Almost surely, 2^21721512 is an apocalyptic number.

It is an amenable number.

21721512 is an abundant number, since it is smaller than the sum of its proper divisors (35777688).

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

21721512 is a wasteful number, since it uses less digits than its factorization.

21721512 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53265 (or 53261 counting only the distinct ones).

The product of its digits is 280, while the sum is 21.

The square root of 21721512 is about 4660.6342915959. The cubic root of 21721512 is about 279.0165841043.

The spelling of 21721512 in words is "twenty-one million, seven hundred twenty-one thousand, five hundred twelve".