21626937721 has 9 divisors (see below), whose sum is σ = 21765614661. Its totient is φ = 21489141564.

The previous prime is 21626937667. The next prime is 21626937727. The reversal of 21626937721 is 12773962612.

The square root of 21626937721 is 147061.

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

It is not a de Polignac number, because 21626937721 - 2²⁷ = 21492719993 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21626937727) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 29264770 + ... + 29265508.

It is an arithmetic number, because the mean of its divisors is an integer number (2418401629).

Almost surely, 2^21626937721 is an apocalyptic number.

21626937721 is the 147061-st square number.

21626937721 is the 73531-st centered octagonal number.

It is an amenable number.

21626937721 is a deficient number, since it is larger than the sum of its proper divisors (138676940).

21626937721 is an frugal number, since it uses more digits than its factorization.

21626937721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1876 (or 938 counting only the distinct ones).

The product of its digits is 381024, while the sum is 46.

The spelling of 21626937721 in words is "twenty-one billion, six hundred twenty-six million, nine hundred thirty-seven thousand, seven hundred twenty-one".