81756417279 has 4 divisors (see below), whose sum is σ = 109008556376. Its totient is φ = 54504278184.

The previous prime is 81756417257. The next prime is 81756417371. The reversal of 81756417279 is 97271465718.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 81756417279 - 2¹¹ = 81756415231 is a prime.

It is a super-2 number, since 2×81756417279² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81756417209) 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, 13626069544 + ... + 13626069549.

It is an arithmetic number, because the mean of its divisors is an integer number (27252139094).

Almost surely, 2^81756417279 is an apocalyptic number.

81756417279 is a deficient number, since it is larger than the sum of its proper divisors (27252139097).

81756417279 is a wasteful number, since it uses less digits than its factorization.

81756417279 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27252139096.

The product of its digits is 5927040, while the sum is 57.

The spelling of 81756417279 in words is "eighty-one billion, seven hundred fifty-six million, four hundred seventeen thousand, two hundred seventy-nine".