81605107583999 has 4 divisors (see below), whose sum is σ = 81626091158880. Its totient is φ = 81584124009120.

The previous prime is 81605107583963. The next prime is 81605107584017. The reversal of 81605107583999 is 99938570150618.

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

It is a cyclic number.

It is not a de Polignac number, because 81605107583999 - 2¹⁶ = 81605107518463 is a prime.

It is a super-2 number, since 2×81605107583999² (a number of 29 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 (81605106583999) 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, 10491781607 + ... + 10491789384.

It is an arithmetic number, because the mean of its divisors is an integer number (20406522789720).

Almost surely, 2^{81605107583999} is an apocalyptic number.

81605107583999 is a deficient number, since it is larger than the sum of its proper divisors (20983574881).

81605107583999 is a wasteful number, since it uses less digits than its factorization.

81605107583999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20983574880.

The product of its (nonzero) digits is 146966400, while the sum is 71.

The spelling of 81605107583999 in words is "eighty-one trillion, six hundred five billion, one hundred seven million, five hundred eighty-three thousand, nine hundred ninety-nine".