91891397 has 4 divisors (see below), whose sum is σ = 98959980. Its totient is φ = 84822816.

The previous prime is 91891367. The next prime is 91891399. The reversal of 91891397 is 79319819.

It is a happy number.

It is a Cunningham number, because it is equal to 9586²+1.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 79319819 = 4027 ⋅19697.

It can be written as a sum of positive squares in 2 ways, for example, as 13586596 + 78304801 = 3686^2 + 8849^2 .

It is not a de Polignac number, because 91891397 - 2¹⁸ = 91629253 is a prime.

It is a super-2 number, since 2×91891397² = 16888057685223218, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91891399) 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, 3534272 + ... + 3534297.

It is an arithmetic number, because the mean of its divisors is an integer number (24739995).

Almost surely, 2^91891397 is an apocalyptic number.

It is an amenable number.

91891397 is a deficient number, since it is larger than the sum of its proper divisors (7068583).

91891397 is a wasteful number, since it uses less digits than its factorization.

91891397 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7068582.

The product of its digits is 122472, while the sum is 47.

The square root of 91891397 is about 9586.0000521594. Note that the first 4 decimals coincide. The cubic root of 91891397 is about 451.2580385459.

The spelling of 91891397 in words is "ninety-one million, eight hundred ninety-one thousand, three hundred ninety-seven".