91720444545 has 48 divisors (see below), whose sum is σ = 168614065152. Its totient is φ = 46023626880.

The previous prime is 91720444511. The next prime is 91720444547. The reversal of 91720444545 is 54544402719.

91720444545 is a `hidden beast` number, since 91 + 72 + 0 + 44 + 454 + 5 = 666.

It is not a de Polignac number, because 91720444545 - 2⁶ = 91720444481 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 91720444545.

It is not an unprimeable number, because it can be changed into a prime (91720444547) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 663249 + ... + 789518.

It is an arithmetic number, because the mean of its divisors is an integer number (3512793024).

Almost surely, 2^91720444545 is an apocalyptic number.

It is an amenable number.

91720444545 is a deficient number, since it is larger than the sum of its proper divisors (76893620607).

91720444545 is a wasteful number, since it uses less digits than its factorization.

91720444545 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1452862 (or 1452859 counting only the distinct ones).

The product of its (nonzero) digits is 806400, while the sum is 45.

The spelling of 91720444545 in words is "ninety-one billion, seven hundred twenty million, four hundred forty-four thousand, five hundred forty-five".