81765694993 has 4 divisors (see below), whose sum is σ = 81787815460. Its totient is φ = 81743574528.

The previous prime is 81765694987. The next prime is 81765695021. The reversal of 81765694993 is 39949656718.

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

It can be written as a sum of positive squares in 2 ways, for example, as 45220873104 + 36544821889 = 212652^2 + 191167^2 .

It is a cyclic number.

It is not a de Polignac number, because 81765694993 - 2²¹ = 81763597841 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81765694943) 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, 11054688 + ... + 11062081.

It is an arithmetic number, because the mean of its divisors is an integer number (20446953865).

Almost surely, 2^81765694993 is an apocalyptic number.

It is an amenable number.

81765694993 is a deficient number, since it is larger than the sum of its proper divisors (22120467).

81765694993 is a wasteful number, since it uses less digits than its factorization.

81765694993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22120466.

The product of its digits is 88179840, while the sum is 67.

The spelling of 81765694993 in words is "eighty-one billion, seven hundred sixty-five million, six hundred ninety-four thousand, nine hundred ninety-three".