91017812781 has 80 divisors (see below), whose sum is σ = 164549468160. Its totient is φ = 48976786080.

The previous prime is 91017812759. The next prime is 91017812791. The reversal of 91017812781 is 18721871019.

It is not a de Polignac number, because 91017812781 - 2²⁶ = 90950703917 is a prime.

It is a super-2 number, since 2×91017812781² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91017812701) by changing a digit.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 1773796 + ... + 1824386.

It is an arithmetic number, because the mean of its divisors is an integer number (2056868352).

Almost surely, 2^91017812781 is an apocalyptic number.

It is an amenable number.

91017812781 is a deficient number, since it is larger than the sum of its proper divisors (73531655379).

91017812781 is a wasteful number, since it uses less digits than its factorization.

91017812781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50796 (or 50787 counting only the distinct ones).

The product of its (nonzero) digits is 56448, while the sum is 45.

The spelling of 91017812781 in words is "ninety-one billion, seventeen million, eight hundred twelve thousand, seven hundred eighty-one".