181991640761 has 16 divisors (see below), whose sum is σ = 220248107136. Its totient is φ = 146801500416.

The previous prime is 181991640757. The next prime is 181991640763. The reversal of 181991640761 is 167046199181.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 181991640761 - 2² = 181991640757 is a prime.

It is not an unprimeable number, because it can be changed into a prime (181991640763) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1147295 + ... + 1296251.

It is an arithmetic number, because the mean of its divisors is an integer number (13765506696).

Almost surely, 2^181991640761 is an apocalyptic number.

It is an amenable number.

181991640761 is a deficient number, since it is larger than the sum of its proper divisors (38256466375).

181991640761 is a wasteful number, since it uses less digits than its factorization.

181991640761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 159248.

The product of its (nonzero) digits is 653184, while the sum is 53.

The spelling of 181991640761 in words is "one hundred eighty-one billion, nine hundred ninety-one million, six hundred forty thousand, seven hundred sixty-one".