91555909 has 2 divisors, whose sum is σ = 91555910. Its totient is φ = 91555908.

The previous prime is 91555907. The next prime is 91555949. The reversal of 91555909 is 90955519.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 68062500 + 23493409 = 8250^2 + 4847^2 .

It is a cyclic number.

It is not a de Polignac number, because 91555909 - 2¹ = 91555907 is a prime.

Together with 91555907, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91555903) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45777954 + 45777955.

It is an arithmetic number, because the mean of its divisors is an integer number (45777955).

Almost surely, 2^91555909 is an apocalyptic number.

It is an amenable number.

91555909 is a deficient number, since it is larger than the sum of its proper divisors (1).

91555909 is an equidigital number, since it uses as much as digits as its factorization.

91555909 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 91125, while the sum is 43.

The square root of 91555909 is about 9568.4851988180. The cubic root of 91555909 is about 450.7082000919.

The spelling of 91555909 in words is "ninety-one million, five hundred fifty-five thousand, nine hundred nine".