81665120189 has 2 divisors, whose sum is σ = 81665120190. Its totient is φ = 81665120188.

The previous prime is 81665120179. The next prime is 81665120233. The reversal of 81665120189 is 98102156618.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 77580632089 + 4084488100 = 278533^2 + 63910^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81665120189 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81665120179) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40832560094 + 40832560095.

It is an arithmetic number, because the mean of its divisors is an integer number (40832560095).

Almost surely, 2^81665120189 is an apocalyptic number.

It is an amenable number.

81665120189 is a deficient number, since it is larger than the sum of its proper divisors (1).

81665120189 is an equidigital number, since it uses as much as digits as its factorization.

81665120189 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 207360, while the sum is 47.

The spelling of 81665120189 in words is "eighty-one billion, six hundred sixty-five million, one hundred twenty thousand, one hundred eighty-nine".