91900981 has 2 divisors, whose sum is σ = 91900982. Its totient is φ = 91900980.

The previous prime is 91900973. The next prime is 91900999. The reversal of 91900981 is 18900919.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 73702225 + 18198756 = 8585^2 + 4266^2 .

It is an emirp because it is prime and its reverse (18900919) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 91900981 - 2³ = 91900973 is a prime.

It is a super-2 number, since 2×91900981² = 16891580617524722, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 91900981.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91900901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45950490 + 45950491.

It is an arithmetic number, because the mean of its divisors is an integer number (45950491).

Almost surely, 2^91900981 is an apocalyptic number.

It is an amenable number.

91900981 is a deficient number, since it is larger than the sum of its proper divisors (1).

91900981 is an equidigital number, since it uses as much as digits as its factorization.

91900981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5832, while the sum is 37.

The square root of 91900981 is about 9586.4999348042. The cubic root of 91900981 is about 451.2737262919.

The spelling of 91900981 in words is "ninety-one million, nine hundred thousand, nine hundred eighty-one".