81745137081 has 12 divisors (see below), whose sum is σ = 120304164708. Its totient is φ = 53468517024.

The previous prime is 81745137077. The next prime is 81745137083. The reversal of 81745137081 is 18073154718.

It can be written as a sum of positive squares in 2 ways, for example, as 61847213481 + 19897923600 = 248691^2 + 141060^2 .

It is not a de Polignac number, because 81745137081 - 2² = 81745137077 is a prime.

It is a super-2 number, since 2×81745137081² (a number of 23 digits) contains 22 as substring.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81745137083) 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, 85686250 + ... + 85687203.

It is an arithmetic number, because the mean of its divisors is an integer number (10025347059).

Almost surely, 2^81745137081 is an apocalyptic number.

It is an amenable number.

81745137081 is a deficient number, since it is larger than the sum of its proper divisors (38559027627).

81745137081 is a wasteful number, since it uses less digits than its factorization.

81745137081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 171373512 (or 171373509 counting only the distinct ones).

The product of its (nonzero) digits is 188160, while the sum is 45.

The spelling of 81745137081 in words is "eighty-one billion, seven hundred forty-five million, one hundred thirty-seven thousand, eighty-one".