20721516 has 48 divisors (see below), whose sum is σ = 50899968. Its totient is φ = 6552000.

The previous prime is 20721511. The next prime is 20721529. The reversal of 20721516 is 61512702.

It is a hoax number, since the sum of its digits (24) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (20721511) 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, 19191 + ... + 20241.

It is an arithmetic number, because the mean of its divisors is an integer number (1060416).

Almost surely, 2^20721516 is an apocalyptic number.

It is an amenable number.

20721516 is an abundant number, since it is smaller than the sum of its proper divisors (30178452).

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

20721516 is a wasteful number, since it uses less digits than its factorization.

20721516 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1142 (or 1140 counting only the distinct ones).

The product of its (nonzero) digits is 840, while the sum is 24.

The square root of 20721516 is about 4552.0891906904. The cubic root of 20721516 is about 274.6674371057.

The spelling of 20721516 in words is "twenty million, seven hundred twenty-one thousand, five hundred sixteen".