91278581 has 2 divisors, whose sum is σ = 91278582. Its totient is φ = 91278580.

The previous prime is 91278569. The next prime is 91278599. The reversal of 91278581 is 18587219.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 84015556 + 7263025 = 9166^2 + 2695^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-91278581 is a prime.

It is a super-2 number, since 2×91278581² = 16663558698747122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91278511) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45639290 + 45639291.

It is an arithmetic number, because the mean of its divisors is an integer number (45639291).

Almost surely, 2^91278581 is an apocalyptic number.

It is an amenable number.

91278581 is a deficient number, since it is larger than the sum of its proper divisors (1).

91278581 is an equidigital number, since it uses as much as digits as its factorization.

91278581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 40320, while the sum is 41.

The square root of 91278581 is about 9553.9824680601. The cubic root of 91278581 is about 450.2526663366.

The spelling of 91278581 in words is "ninety-one million, two hundred seventy-eight thousand, five hundred eighty-one".