81116439637 has 2 divisors, whose sum is σ = 81116439638. Its totient is φ = 81116439636.

The previous prime is 81116439611. The next prime is 81116439673. The reversal of 81116439637 is 73693461118.

Together with next prime (81116439673) 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., 45576272196 + 35540167441 = 213486^2 + 188521^2 .

It is a cyclic number.

It is not a de Polignac number, because 81116439637 - 2³⁵ = 46756701269 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81116439337) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40558219818 + 40558219819.

It is an arithmetic number, because the mean of its divisors is an integer number (40558219819).

Almost surely, 2^81116439637 is an apocalyptic number.

It is an amenable number.

81116439637 is a deficient number, since it is larger than the sum of its proper divisors (1).

81116439637 is an equidigital number, since it uses as much as digits as its factorization.

81116439637 is an evil number, because the sum of its binary digits is even.

The product of its digits is 653184, while the sum is 49.

The spelling of 81116439637 in words is "eighty-one billion, one hundred sixteen million, four hundred thirty-nine thousand, six hundred thirty-seven".