91215617997 has 8 divisors (see below), whose sum is σ = 138995227456. Its totient is φ = 52123210272.

The previous prime is 91215617971. The next prime is 91215618029. The reversal of 91215617997 is 79971651219.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 91215617997 - 2¹² = 91215613901 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91215617947) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2171800408 + ... + 2171800449.

It is an arithmetic number, because the mean of its divisors is an integer number (17374403432).

Almost surely, 2^91215617997 is an apocalyptic number.

It is an amenable number.

91215617997 is a deficient number, since it is larger than the sum of its proper divisors (47779609459).

91215617997 is a wasteful number, since it uses less digits than its factorization.

91215617997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4343600867.

The product of its digits is 2143260, while the sum is 57.

The spelling of 91215617997 in words is "ninety-one billion, two hundred fifteen million, six hundred seventeen thousand, nine hundred ninety-seven".