81308137 has 2 divisors, whose sum is σ = 81308138. Its totient is φ = 81308136.

The previous prime is 81308119. The next prime is 81308173. The reversal of 81308137 is 73180318.

Together with next prime (81308173) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 81288256 + 19881 = 9016^2 + 141^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81308137 is a prime.

It is a super-2 number, since 2×81308137² = 13222026284821538, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 81308099 and 81308108.

It is not a weakly prime, because it can be changed into another prime (81308177) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40654068 + 40654069.

It is an arithmetic number, because the mean of its divisors is an integer number (40654069).

Almost surely, 2^81308137 is an apocalyptic number.

It is an amenable number.

81308137 is a deficient number, since it is larger than the sum of its proper divisors (1).

81308137 is an equidigital number, since it uses as much as digits as its factorization.

81308137 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4032, while the sum is 31.

The square root of 81308137 is about 9017.1024725241. The cubic root of 81308137 is about 433.2228317189. Note that the first 3 decimals are identical.

The spelling of 81308137 in words is "eighty-one million, three hundred eight thousand, one hundred thirty-seven".