91899781 has 2 divisors, whose sum is σ = 91899782. Its totient is φ = 91899780.

The previous prime is 91899719. The next prime is 91899803. The reversal of 91899781 is 18799819.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 91872225 + 27556 = 9585^2 + 166^2 .

It is a cyclic number.

It is not a de Polignac number, because 91899781 - 2⁷ = 91899653 is a prime.

It is a super-2 number, since 2×91899781² = 16891139495695922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91899281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45949890 + 45949891.

It is an arithmetic number, because the mean of its divisors is an integer number (45949891).

Almost surely, 2^91899781 is an apocalyptic number.

It is an amenable number.

91899781 is a deficient number, since it is larger than the sum of its proper divisors (1).

91899781 is an equidigital number, since it uses as much as digits as its factorization.

91899781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 326592, while the sum is 52.

The square root of 91899781 is about 9586.4373465850. The cubic root of 91899781 is about 451.2717621097.

The spelling of 91899781 in words is "ninety-one million, eight hundred ninety-nine thousand, seven hundred eighty-one".