91721197 has 4 divisors (see below), whose sum is σ = 91758496. Its totient is φ = 91683900.

The previous prime is 91721177. The next prime is 91721213. The reversal of 91721197 is 79112719.

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, and also an emirpimes, since its reverse is a distinct semiprime: 79112719 = 7 ⋅11301817.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-91721197 is a prime.

It is a super-2 number, since 2×91721197² = 16825555958225618, 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 (91721117) 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, 14679 + ... + 19972.

It is an arithmetic number, because the mean of its divisors is an integer number (22939624).

Almost surely, 2^91721197 is an apocalyptic number.

It is an amenable number.

91721197 is a deficient number, since it is larger than the sum of its proper divisors (37299).

91721197 is a wasteful number, since it uses less digits than its factorization.

91721197 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37298.

The product of its digits is 7938, while the sum is 37.

The square root of 91721197 is about 9577.1184079555. The cubic root of 91721197 is about 450.9792616852.

The spelling of 91721197 in words is "ninety-one million, seven hundred twenty-one thousand, one hundred ninety-seven".