91781065 has 4 divisors (see below), whose sum is σ = 110137284. Its totient is φ = 73424848.

The previous prime is 91781057. The next prime is 91781071. The reversal of 91781065 is 56018719.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 56018719 = 359 ⋅156041.

It can be written as a sum of positive squares in 2 ways, for example, as 25130169 + 66650896 = 5013^2 + 8164^2 .

It is a cyclic number.

It is not a de Polignac number, because 91781065 - 2³ = 91781057 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9178102 + ... + 9178111.

It is an arithmetic number, because the mean of its divisors is an integer number (27534321).

Almost surely, 2^91781065 is an apocalyptic number.

It is an amenable number.

91781065 is a deficient number, since it is larger than the sum of its proper divisors (18356219).

91781065 is a wasteful number, since it uses less digits than its factorization.

91781065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18356218.

The product of its (nonzero) digits is 15120, while the sum is 37.

The square root of 91781065 is about 9580.2434728978. The cubic root of 91781065 is about 451.0773609802.

The spelling of 91781065 in words is "ninety-one million, seven hundred eighty-one thousand, sixty-five".