91208216557 has 2 divisors, whose sum is σ = 91208216558. Its totient is φ = 91208216556.

The previous prime is 91208216551. The next prime is 91208216579. The reversal of 91208216557 is 75561280219.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 85477877956 + 5730338601 = 292366^2 + 75699^2 .

It is a cyclic number.

It is not a de Polignac number, because 91208216557 - 2¹⁹ = 91207692269 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91208216551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45604108278 + 45604108279.

It is an arithmetic number, because the mean of its divisors is an integer number (45604108279).

Almost surely, 2^91208216557 is an apocalyptic number.

It is an amenable number.

91208216557 is a deficient number, since it is larger than the sum of its proper divisors (1).

91208216557 is an equidigital number, since it uses as much as digits as its factorization.

91208216557 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 302400, while the sum is 46.

The spelling of 91208216557 in words is "ninety-one billion, two hundred eight million, two hundred sixteen thousand, five hundred fifty-seven".