81798772187 has 4 divisors (see below), whose sum is σ = 89235024216. Its totient is φ = 74362520160.

The previous prime is 81798772171. The next prime is 81798772189. The reversal of 81798772187 is 78127789718.

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 81798772187 - 2⁴ = 81798772171 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81798772189) 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, 3718125998 + ... + 3718126019.

It is an arithmetic number, because the mean of its divisors is an integer number (22308756054).

Almost surely, 2^81798772187 is an apocalyptic number.

81798772187 is a deficient number, since it is larger than the sum of its proper divisors (7436252029).

81798772187 is a wasteful number, since it uses less digits than its factorization.

81798772187 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7436252028.

The product of its digits is 22127616, while the sum is 65.

The spelling of 81798772187 in words is "eighty-one billion, seven hundred ninety-eight million, seven hundred seventy-two thousand, one hundred eighty-seven".