91278569 has 2 divisors, whose sum is σ = 91278570. Its totient is φ = 91278568.

The previous prime is 91278553. The next prime is 91278581. The reversal of 91278569 is 96587219.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 49843600 + 41434969 = 7060^2 + 6437^2 .

It is an emirp because it is prime and its reverse (96587219) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 91278569 - 2⁴ = 91278553 is a prime.

It is a super-2 number, since 2×91278569² = 16663554317375522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (91278529) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45639284 + 45639285.

It is an arithmetic number, because the mean of its divisors is an integer number (45639285).

Almost surely, 2^91278569 is an apocalyptic number.

It is an amenable number.

91278569 is a deficient number, since it is larger than the sum of its proper divisors (1).

91278569 is an equidigital number, since it uses as much as digits as its factorization.

91278569 is an evil number, because the sum of its binary digits is even.

The product of its digits is 272160, while the sum is 47.

The square root of 91278569 is about 9553.9818400497. The cubic root of 91278569 is about 450.2526466057.

The spelling of 91278569 in words is "ninety-one million, two hundred seventy-eight thousand, five hundred sixty-nine".