81129740189 has 2 divisors, whose sum is σ = 81129740190. Its totient is φ = 81129740188.

The previous prime is 81129740179. The next prime is 81129740233. The reversal of 81129740189 is 98104792118.

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., 81108192025 + 21548164 = 284795^2 + 4642^2 .

It is a cyclic number.

It is not a de Polignac number, because 81129740189 - 2²⁰ = 81128691613 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81129740179) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40564870094 + 40564870095.

It is an arithmetic number, because the mean of its divisors is an integer number (40564870095).

Almost surely, 2^81129740189 is an apocalyptic number.

It is an amenable number.

81129740189 is a deficient number, since it is larger than the sum of its proper divisors (1).

81129740189 is an equidigital number, since it uses as much as digits as its factorization.

81129740189 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 290304, while the sum is 50.

The spelling of 81129740189 in words is "eighty-one billion, one hundred twenty-nine million, seven hundred forty thousand, one hundred eighty-nine".