91439809 has 2 divisors, whose sum is σ = 91439810. Its totient is φ = 91439808.

The previous prime is 91439779. The next prime is 91439827. The reversal of 91439809 is 90893419.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 79709184 + 11730625 = 8928^2 + 3425^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-91439809 is a prime.

It is a super-2 number, since 2×91439809² = 16722477339912962, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (91439849) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45719904 + 45719905.

It is an arithmetic number, because the mean of its divisors is an integer number (45719905).

Almost surely, 2^91439809 is an apocalyptic number.

It is an amenable number.

91439809 is a deficient number, since it is larger than the sum of its proper divisors (1).

91439809 is an equidigital number, since it uses as much as digits as its factorization.

91439809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 69984, while the sum is 43.

The square root of 91439809 is about 9562.4164832954. The cubic root of 91439809 is about 450.5176085123.

The spelling of 91439809 in words is "ninety-one million, four hundred thirty-nine thousand, eight hundred nine".