81139238129 has 2 divisors, whose sum is σ = 81139238130. Its totient is φ = 81139238128.

The previous prime is 81139238099. The next prime is 81139238177. The reversal of 81139238129 is 92183293118.

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., 80870278129 + 268960000 = 284377^2 + 16400^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81139238129 is a prime.

It is not a weakly prime, because it can be changed into another prime (81139238029) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40569619064 + 40569619065.

It is an arithmetic number, because the mean of its divisors is an integer number (40569619065).

Almost surely, 2^81139238129 is an apocalyptic number.

It is an amenable number.

81139238129 is a deficient number, since it is larger than the sum of its proper divisors (1).

81139238129 is an equidigital number, since it uses as much as digits as its factorization.

81139238129 is an evil number, because the sum of its binary digits is even.

The product of its digits is 186624, while the sum is 47.

The spelling of 81139238129 in words is "eighty-one billion, one hundred thirty-nine million, two hundred thirty-eight thousand, one hundred twenty-nine".