91125721 has 4 divisors (see below), whose sum is σ = 91671552. Its totient is φ = 90579892.

The previous prime is 91125719. The next prime is 91125737. The reversal of 91125721 is 12752119.

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: 12752119 = 199 ⋅64081.

It is a cyclic number.

It is not a de Polignac number, because 91125721 - 2¹ = 91125719 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 91125721.

It is not an unprimeable number, because it can be changed into a prime (91122721) 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, 272665 + ... + 272998.

It is an arithmetic number, because the mean of its divisors is an integer number (22917888).

Almost surely, 2^91125721 is an apocalyptic number.

It is an amenable number.

91125721 is a deficient number, since it is larger than the sum of its proper divisors (545831).

91125721 is a wasteful number, since it uses less digits than its factorization.

91125721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 545830.

The product of its digits is 1260, while the sum is 28.

The square root of 91125721 is about 9545.9793106836. The cubic root of 91125721 is about 450.0011868281.

It can be divided in two parts, 9 and 1125721, that multiplied together give a square (10131489 = 3183²).

The spelling of 91125721 in words is "ninety-one million, one hundred twenty-five thousand, seven hundred twenty-one".