78721117 has 6 divisors (see below), whose sum is σ = 79518554. Its totient is φ = 77931600.

The previous prime is 78721091. The next prime is 78721127. The reversal of 78721117 is 71112787.

It can be written as a sum of positive squares in 3 ways, for example, as 53860921 + 24860196 = 7339^2 + 4986^2 .

It is not a de Polignac number, because 78721117 - 2⁷ = 78720989 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78721127) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 6343 + ... + 14059.

Almost surely, 2^78721117 is an apocalyptic number.

It is an amenable number.

78721117 is a deficient number, since it is larger than the sum of its proper divisors (797437).

78721117 is an equidigital number, since it uses as much as digits as its factorization.

78721117 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7919 (or 7818 counting only the distinct ones).

The product of its digits is 5488, while the sum is 34.

The square root of 78721117 is about 8872.4921527156. The cubic root of 78721117 is about 428.5785349668.

It can be divided in two parts, 787 and 21117, that added together give a square (21904 = 148²).

The spelling of 78721117 in words is "seventy-eight million, seven hundred twenty-one thousand, one hundred seventeen".