72649387418521 has 3 divisors (see below), whose sum is σ = 72649395941983. Its totient is φ = 72649378895060.

The previous prime is 72649387418519. The next prime is 72649387418533. The reversal of 72649387418521 is 12581478394627.

The square root of 72649387418521 is 8523461.

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 can be written as a sum of positive squares in only one way, i.e., 67683709994121 + 4965677424400 = 8227011^2 + 2228380^2 .

It is not a de Polignac number, because 72649387418521 - 2¹ = 72649387418519 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (72649387418921) 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, 4261731 + ... + 12785191.

Almost surely, 2^{72649387418521} is an apocalyptic number.

72649387418521 is the 8523461-st square number.

72649387418521 is the 4261731-st centered octagonal number.

It is an amenable number.

72649387418521 is a deficient number, since it is larger than the sum of its proper divisors (8523462).

72649387418521 is an frugal number, since it uses more digits than its factorization.

72649387418521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17046922 (or 8523461 counting only the distinct ones).

The product of its digits is 162570240, while the sum is 67.

The spelling of 72649387418521 in words is "seventy-two trillion, six hundred forty-nine billion, three hundred eighty-seven million, four hundred eighteen thousand, five hundred twenty-one".