21700530721 has 3 divisors (see below), whose sum is σ = 21700678033. Its totient is φ = 21700383410.

The previous prime is 21700530713. The next prime is 21700530739. The reversal of 21700530721 is 12703500712.

The square root of 21700530721 is 147311.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is not a de Polignac number, because 21700530721 - 2³ = 21700530713 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21700530721.

It is not an unprimeable number, because it can be changed into a prime (21700530221) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 73656 + ... + 220966.

Almost surely, 2^21700530721 is an apocalyptic number.

21700530721 is the 147311-st square number.

21700530721 is the 73656-th centered octagonal number.

It is an amenable number.

21700530721 is a deficient number, since it is larger than the sum of its proper divisors (147312).

21700530721 is an frugal number, since it uses more digits than its factorization.

21700530721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 294622 (or 147311 counting only the distinct ones).

The product of its (nonzero) digits is 2940, while the sum is 28.

The spelling of 21700530721 in words is "twenty-one billion, seven hundred million, five hundred thirty thousand, seven hundred twenty-one".