81906906139 has 2 divisors, whose sum is σ = 81906906140. Its totient is φ = 81906906138.

The previous prime is 81906906047. The next prime is 81906906161. The reversal of 81906906139 is 93160960918.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81906906139 - 2⁹ = 81906905627 is a prime.

It is not a weakly prime, because it can be changed into another prime (81906903139) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40953453069 + 40953453070.

It is an arithmetic number, because the mean of its divisors is an integer number (40953453070).

Almost surely, 2^81906906139 is an apocalyptic number.

81906906139 is a deficient number, since it is larger than the sum of its proper divisors (1).

81906906139 is an equidigital number, since it uses as much as digits as its factorization.

81906906139 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 629856, while the sum is 52.

The spelling of 81906906139 in words is "eighty-one billion, nine hundred six million, nine hundred six thousand, one hundred thirty-nine".