91272721 has 4 divisors (see below), whose sum is σ = 91433700. Its totient is φ = 91111744.

The previous prime is 91272719. The next prime is 91272733. The reversal of 91272721 is 12727219.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12727219 = 2111 ⋅6029.

It can be written as a sum of positive squares in 2 ways, for example, as 18835600 + 72437121 = 4340^2 + 8511^2 .

It is a cyclic number.

It is not a de Polignac number, because 91272721 - 2¹ = 91272719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (91272761) 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, 79636 + ... + 80773.

It is an arithmetic number, because the mean of its divisors is an integer number (22858425).

Almost surely, 2^91272721 is an apocalyptic number.

It is an amenable number.

91272721 is a deficient number, since it is larger than the sum of its proper divisors (160979).

91272721 is a wasteful number, since it uses less digits than its factorization.

91272721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 160978.

The product of its digits is 3528, while the sum is 31.

The square root of 91272721 is about 9553.6757847438. The cubic root of 91272721 is about 450.2430308630.

The spelling of 91272721 in words is "ninety-one million, two hundred seventy-two thousand, seven hundred twenty-one".