91231009 has 2 divisors, whose sum is σ = 91231010. Its totient is φ = 91231008.

The previous prime is 91230961. The next prime is 91231033. The reversal of 91231009 is 90013219.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 87609600 + 3621409 = 9360^2 + 1903^2 .

It is a cyclic number.

It is not a de Polignac number, because 91231009 - 2²³ = 82842401 is a prime.

It is not a weakly prime, because it can be changed into another prime (91231039) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45615504 + 45615505.

It is an arithmetic number, because the mean of its divisors is an integer number (45615505).

Almost surely, 2^91231009 is an apocalyptic number.

It is an amenable number.

91231009 is a deficient number, since it is larger than the sum of its proper divisors (1).

91231009 is an equidigital number, since it uses as much as digits as its factorization.

91231009 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 486, while the sum is 25.

The square root of 91231009 is about 9551.4925011749. The cubic root of 91231009 is about 450.1744327877.

The spelling of 91231009 in words is "ninety-one million, two hundred thirty-one thousand, nine".