91127978197 has 2 divisors, whose sum is σ = 91127978198. Its totient is φ = 91127978196.

The previous prime is 91127978189. The next prime is 91127978209. The reversal of 91127978197 is 79187972119.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 90427105521 + 700872676 = 300711^2 + 26474^2 .

It is a cyclic number.

It is not a de Polignac number, because 91127978197 - 2³ = 91127978189 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91127976197) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45563989098 + 45563989099.

It is an arithmetic number, because the mean of its divisors is an integer number (45563989099).

Almost surely, 2^91127978197 is an apocalyptic number.

It is an amenable number.

91127978197 is a deficient number, since it is larger than the sum of its proper divisors (1).

91127978197 is an equidigital number, since it uses as much as digits as its factorization.

91127978197 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4000752, while the sum is 61.

The spelling of 91127978197 in words is "ninety-one billion, one hundred twenty-seven million, nine hundred seventy-eight thousand, one hundred ninety-seven".