81457997557 has 4 divisors (see below), whose sum is σ = 81475698880. Its totient is φ = 81440296236.

The previous prime is 81457997519. The next prime is 81457997563. The reversal of 81457997557 is 75579975418.

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: 75579975418 = 2 ⋅37789987709.

It is a cyclic number.

It is not a de Polignac number, because 81457997557 - 2¹⁹ = 81457473269 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81457997492 and 81457997501.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81457997567) 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, 8843757 + ... + 8852962.

It is an arithmetic number, because the mean of its divisors is an integer number (20368924720).

Almost surely, 2^81457997557 is an apocalyptic number.

It is an amenable number.

81457997557 is a deficient number, since it is larger than the sum of its proper divisors (17701323).

81457997557 is a wasteful number, since it uses less digits than its factorization.

81457997557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17701322.

The product of its digits is 111132000, while the sum is 67.

The spelling of 81457997557 in words is "eighty-one billion, four hundred fifty-seven million, nine hundred ninety-seven thousand, five hundred fifty-seven".