91997257 has 4 divisors (see below), whose sum is σ = 100360656. Its totient is φ = 83633860.

The previous prime is 91997249. The next prime is 91997267. The reversal of 91997257 is 75279919.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 91997257 - 2³ = 91997249 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 91997257.

It is not an unprimeable number, because it can be changed into a prime (91997267) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4181683 + ... + 4181704.

It is an arithmetic number, because the mean of its divisors is an integer number (25090164).

Almost surely, 2^91997257 is an apocalyptic number.

It is an amenable number.

91997257 is a deficient number, since it is larger than the sum of its proper divisors (8363399).

91997257 is a wasteful number, since it uses less digits than its factorization.

91997257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8363398.

The product of its digits is 357210, while the sum is 49.

The square root of 91997257 is about 9591.5200568002. The cubic root of 91997257 is about 451.4312569512.

It can be divided in two parts, 919972 and 57, that added together give a palindrome (920029).

The spelling of 91997257 in words is "ninety-one million, nine hundred ninety-seven thousand, two hundred fifty-seven".