78517881 has 12 divisors (see below), whose sum is σ = 122139108. Its totient is φ = 48318624.

The previous prime is 78517853. The next prime is 78517897. The reversal of 78517881 is 18871587.

It can be written as a sum of positive squares in 2 ways, for example, as 38638656 + 39879225 = 6216^2 + 6315^2 .

It is not a de Polignac number, because 78517881 - 2⁷ = 78517753 is a prime.

It is a super-2 number, since 2×78517881² = 12330115273460322, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (78517381) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 335430 + ... + 335663.

It is an arithmetic number, because the mean of its divisors is an integer number (10178259).

Almost surely, 2^78517881 is an apocalyptic number.

It is an amenable number.

78517881 is a deficient number, since it is larger than the sum of its proper divisors (43621227).

78517881 is a wasteful number, since it uses less digits than its factorization.

78517881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 671112 (or 671109 counting only the distinct ones).

The product of its digits is 125440, while the sum is 45.

The square root of 78517881 is about 8861.0315990860. The cubic root of 78517881 is about 428.2093936387.

The spelling of 78517881 in words is "seventy-eight million, five hundred seventeen thousand, eight hundred eighty-one".