91680781 has 2 divisors, whose sum is σ = 91680782. Its totient is φ = 91680780.

The previous prime is 91680763. The next prime is 91680791. The reversal of 91680781 is 18708619.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 59814756 + 31866025 = 7734^2 + 5645^2 .

It is a cyclic number.

It is not a de Polignac number, because 91680781 - 2⁷ = 91680653 is a prime.

It is a super-2 number, since 2×91680781² = 16810731209539922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91680731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45840390 + 45840391.

It is an arithmetic number, because the mean of its divisors is an integer number (45840391).

Almost surely, 2^91680781 is an apocalyptic number.

It is an amenable number.

91680781 is a deficient number, since it is larger than the sum of its proper divisors (1).

91680781 is an equidigital number, since it uses as much as digits as its factorization.

91680781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 24192, while the sum is 40.

The square root of 91680781 is about 9575.0081462106. The cubic root of 91680781 is about 450.9130121659.

The spelling of 91680781 in words is "ninety-one million, six hundred eighty thousand, seven hundred eighty-one".