91720038537 has 12 divisors (see below), whose sum is σ = 132902436420. Its totient is φ = 60953798688.

The previous prime is 91720038523. The next prime is 91720038547. The reversal of 91720038537 is 73583002719.

It is a happy number.

91720038537 is a `hidden beast` number, since 91 + 7 + 20 + 0 + 3 + 8 + 537 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 28717030521 + 63003008016 = 169461^2 + 251004^2 .

It is not a de Polignac number, because 91720038537 - 2¹¹ = 91720036489 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 91720038492 and 91720038501.

It is not an unprimeable number, because it can be changed into a prime (91720038547) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 16071462 + ... + 16077167.

It is an arithmetic number, because the mean of its divisors is an integer number (11075203035).

Almost surely, 2^91720038537 is an apocalyptic number.

It is an amenable number.

91720038537 is a deficient number, since it is larger than the sum of its proper divisors (41182397883).

91720038537 is a wasteful number, since it uses less digits than its factorization.

91720038537 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32148952 (or 32148949 counting only the distinct ones).

The product of its (nonzero) digits is 317520, while the sum is 45.

The spelling of 91720038537 in words is "ninety-one billion, seven hundred twenty million, thirty-eight thousand, five hundred thirty-seven".