78225936721 has 3 divisors (see below), whose sum is σ = 78226216411. Its totient is φ = 78225657032.

The previous prime is 78225936643. The next prime is 78225936727. The reversal of 78225936721 is 12763952287.

It is a happy number.

The square root of 78225936721 is 279689.

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, and also an emirpimes, since its reverse is a distinct semiprime: 12763952287 = 35317 ⋅361411.

It can be written as a sum of positive squares in only one way, i.e., 763914321 + 77462022400 = 27639^2 + 278320^2 .

It is not a de Polignac number, because 78225936721 - 2¹⁷ = 78225805649 is a prime.

It is a super-2 number, since 2×78225936721² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78225936727) 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, 139845 + ... + 419533.

Almost surely, 2^78225936721 is an apocalyptic number.

78225936721 is the 279689-th square number.

78225936721 is the 139845-th centered octagonal number.

It is an amenable number.

78225936721 is a deficient number, since it is larger than the sum of its proper divisors (279690).

78225936721 is an frugal number, since it uses more digits than its factorization.

78225936721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 559378 (or 279689 counting only the distinct ones).

The product of its digits is 2540160, while the sum is 52.

The spelling of 78225936721 in words is "seventy-eight billion, two hundred twenty-five million, nine hundred thirty-six thousand, seven hundred twenty-one".