79784216521 has 3 divisors (see below), whose sum is σ = 79784498983. Its totient is φ = 79783934060.

The previous prime is 79784216507. The next prime is 79784216527. The reversal of 79784216521 is 12561248797.

The square root of 79784216521 is 282461.

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., 24793966521 + 54990250000 = 157461^2 + 234500^2 .

It is not a de Polignac number, because 79784216521 - 2²¹ = 79782119369 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (79784216527) 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, 141231 + ... + 423691.

Almost surely, 2^79784216521 is an apocalyptic number.

79784216521 is the 282461-st square number.

79784216521 is the 141231-st centered octagonal number.

It is an amenable number.

79784216521 is a deficient number, since it is larger than the sum of its proper divisors (282462).

79784216521 is an frugal number, since it uses more digits than its factorization.

79784216521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 564922 (or 282461 counting only the distinct ones).

The product of its digits is 1693440, while the sum is 52.

The spelling of 79784216521 in words is "seventy-nine billion, seven hundred eighty-four million, two hundred sixteen thousand, five hundred twenty-one".