8399337181921 has 81 divisors (see below), whose sum is σ = 10463199290481. Its totient is φ = 6722296032144.

The previous prime is 8399337181891. The next prime is 8399337181957. The reversal of 8399337181921 is 1291817339938.

The square root of 8399337181921 is 2898161.

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

It is not a de Polignac number, because 8399337181921 - 2⁹ = 8399337181409 is a prime.

It is not an unprimeable number, because it can be changed into a prime (8399337151921) by changing a digit.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 21930384096 + ... + 21930384478.

Almost surely, 2^{8399337181921} is an apocalyptic number.

8399337181921 is the 2898161-st square number.

8399337181921 is the 1449081-st centered octagonal number.

It is an amenable number.

8399337181921 is a deficient number, since it is larger than the sum of its proper divisors (2063862108560).

8399337181921 is an frugal number, since it uses more digits than its factorization.

8399337181921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 920 (or 460 counting only the distinct ones).

The product of its digits is 17635968, while the sum is 64.

Multiplying 8399337181921 by its sum of digits (64), we get a square (537557579642944 = 23185288²).

The spelling of 8399337181921 in words is "eight trillion, three hundred ninety-nine billion, three hundred thirty-seven million, one hundred eighty-one thousand, nine hundred twenty-one".