91987381 has 2 divisors, whose sum is σ = 91987382. Its totient is φ = 91987380.

The previous prime is 91987367. The next prime is 91987403. The reversal of 91987381 is 18378919.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 91987281 + 100 = 9591^2 + 10^2 .

It is a cyclic number.

It is not a de Polignac number, because 91987381 - 2⁷ = 91987253 is a prime.

It is a super-2 number, since 2×91987381² = 16923356526478322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91987321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45993690 + 45993691.

It is an arithmetic number, because the mean of its divisors is an integer number (45993691).

Almost surely, 2^91987381 is an apocalyptic number.

It is an amenable number.

91987381 is a deficient number, since it is larger than the sum of its proper divisors (1).

91987381 is an equidigital number, since it uses as much as digits as its factorization.

91987381 is an evil number, because the sum of its binary digits is even.

The product of its digits is 108864, while the sum is 46.

The square root of 91987381 is about 9591.0052132193. The cubic root of 91987381 is about 451.4151025035.

The spelling of 91987381 in words is "ninety-one million, nine hundred eighty-seven thousand, three hundred eighty-one".