91856581 has 2 divisors, whose sum is σ = 91856582. Its totient is φ = 91856580.

The previous prime is 91856561. The next prime is 91856591. The reversal of 91856581 is 18565819.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 62252100 + 29604481 = 7890^2 + 5441^2 .

It is a cyclic number.

It is not a de Polignac number, because 91856581 - 2¹³ = 91848389 is a prime.

It is a super-2 number, since 2×91856581² = 16875262946019122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91856551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45928290 + 45928291.

It is an arithmetic number, because the mean of its divisors is an integer number (45928291).

Almost surely, 2^91856581 is an apocalyptic number.

It is an amenable number.

91856581 is a deficient number, since it is larger than the sum of its proper divisors (1).

91856581 is an equidigital number, since it uses as much as digits as its factorization.

91856581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 86400, while the sum is 43.

The square root of 91856581 is about 9584.1838984861. The cubic root of 91856581 is about 451.2010401579.

The spelling of 91856581 in words is "ninety-one million, eight hundred fifty-six thousand, five hundred eighty-one".