81128137757 has 8 divisors (see below), whose sum is σ = 81484767672. Its totient is φ = 80771673600.

The previous prime is 81128137723. The next prime is 81128137771. The reversal of 81128137757 is 75773182118.

It can be written as a sum of positive squares in 4 ways, for example, as 32280949561 + 48847188196 = 179669^2 + 221014^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81128137757 - 2¹² = 81128133661 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81128137957) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 996407 + ... + 1074747.

It is an arithmetic number, because the mean of its divisors is an integer number (10185595959).

Almost surely, 2^81128137757 is an apocalyptic number.

It is an amenable number.

81128137757 is a deficient number, since it is larger than the sum of its proper divisors (356629915).

81128137757 is a wasteful number, since it uses less digits than its factorization.

81128137757 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82879.

The product of its digits is 658560, while the sum is 50.

The spelling of 81128137757 in words is "eighty-one billion, one hundred twenty-eight million, one hundred thirty-seven thousand, seven hundred fifty-seven".