91981777 has 2 divisors, whose sum is σ = 91981778. Its totient is φ = 91981776.

The previous prime is 91981759. The next prime is 91981789. The reversal of 91981777 is 77718919.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 53056656 + 38925121 = 7284^2 + 6239^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-91981777 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 91981777.

It is not a weakly prime, because it can be changed into another prime (91951777) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45990888 + 45990889.

It is an arithmetic number, because the mean of its divisors is an integer number (45990889).

Almost surely, 2^91981777 is an apocalyptic number.

It is an amenable number.

91981777 is a deficient number, since it is larger than the sum of its proper divisors (1).

91981777 is an equidigital number, since it uses as much as digits as its factorization.

91981777 is an evil number, because the sum of its binary digits is even.

The product of its digits is 222264, while the sum is 49.

The square root of 91981777 is about 9590.7130600389. The cubic root of 91981777 is about 451.4059353707.

The spelling of 91981777 in words is "ninety-one million, nine hundred eighty-one thousand, seven hundred seventy-seven".