81906906161 has 2 divisors, whose sum is σ = 81906906162. Its totient is φ = 81906906160.

The previous prime is 81906906139. The next prime is 81906906203. The reversal of 81906906161 is 16160960918.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 81770833936 + 136072225 = 285956^2 + 11665^2 .

It is a cyclic number.

It is not a de Polignac number, because 81906906161 - 2¹⁰ = 81906905137 is a prime.

It is not a weakly prime, because it can be changed into another prime (81906926161) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40953453080 + 40953453081.

It is an arithmetic number, because the mean of its divisors is an integer number (40953453081).

Almost surely, 2^81906906161 is an apocalyptic number.

It is an amenable number.

81906906161 is a deficient number, since it is larger than the sum of its proper divisors (1).

81906906161 is an equidigital number, since it uses as much as digits as its factorization.

81906906161 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 139968, while the sum is 47.

The spelling of 81906906161 in words is "eighty-one billion, nine hundred six million, nine hundred six thousand, one hundred sixty-one".