91137785857 has 4 divisors (see below), whose sum is σ = 91185429060. Its totient is φ = 91090142656.

The previous prime is 91137785839. The next prime is 91137785897. The reversal of 91137785857 is 75858773119.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 75858773119 = 145303 ⋅522073.

It can be written as a sum of positive squares in 2 ways, for example, as 42141520656 + 48996265201 = 205284^2 + 221351^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-91137785857 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 91137785795 and 91137785804.

It is not an unprimeable number, because it can be changed into a prime (91137785897) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23818732 + ... + 23822557.

It is an arithmetic number, because the mean of its divisors is an integer number (22796357265).

Almost surely, 2^91137785857 is an apocalyptic number.

It is an amenable number.

91137785857 is a deficient number, since it is larger than the sum of its proper divisors (47643203).

91137785857 is a wasteful number, since it uses less digits than its factorization.

91137785857 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47643202.

The product of its digits is 14817600, while the sum is 61.

The spelling of 91137785857 in words is "ninety-one billion, one hundred thirty-seven million, seven hundred eighty-five thousand, eight hundred fifty-seven".