81188397769 has 4 divisors (see below), whose sum is σ = 81210185344. Its totient is φ = 81166610196.

The previous prime is 81188397757. The next prime is 81188397841. The reversal of 81188397769 is 96779388118.

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.

It is a cyclic number.

It is not a de Polignac number, because 81188397769 - 2²³ = 81180009161 is a prime.

It is a super-2 number, since 2×81188397769² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81188397749) 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, 10888197 + ... + 10895650.

It is an arithmetic number, because the mean of its divisors is an integer number (20302546336).

Almost surely, 2^81188397769 is an apocalyptic number.

It is an amenable number.

81188397769 is a deficient number, since it is larger than the sum of its proper divisors (21787575).

81188397769 is a wasteful number, since it uses less digits than its factorization.

81188397769 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21787574.

The product of its digits is 36578304, while the sum is 67.

The spelling of 81188397769 in words is "eighty-one billion, one hundred eighty-eight million, three hundred ninety-seven thousand, seven hundred sixty-nine".