91573705781 has 4 divisors (see below), whose sum is σ = 91624272864. Its totient is φ = 91523138700.

The previous prime is 91573705759. The next prime is 91573705823. The reversal of 91573705781 is 18750737519.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 18750737519 = 36529 ⋅513311.

It is a cyclic number.

It is not a de Polignac number, because 91573705781 - 2³⁴ = 74393836597 is a prime.

It is a super-2 number, since 2×91573705781² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91573705711) 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, 25280825 + ... + 25284446.

It is an arithmetic number, because the mean of its divisors is an integer number (22906068216).

Almost surely, 2^91573705781 is an apocalyptic number.

It is an amenable number.

91573705781 is a deficient number, since it is larger than the sum of its proper divisors (50567083).

91573705781 is a wasteful number, since it uses less digits than its factorization.

91573705781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50567082.

The product of its (nonzero) digits is 1852200, while the sum is 53.

The spelling of 91573705781 in words is "ninety-one billion, five hundred seventy-three million, seven hundred five thousand, seven hundred eighty-one".