81865367531 has 2 divisors, whose sum is σ = 81865367532. Its totient is φ = 81865367530.

The previous prime is 81865367513. The next prime is 81865367539. The reversal of 81865367531 is 13576356818.

It is a happy number.

Together with previous prime (81865367513) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81865367531 is a prime.

It is a super-2 number, since 2×81865367531² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81865367539) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40932683765 + 40932683766.

It is an arithmetic number, because the mean of its divisors is an integer number (40932683766).

Almost surely, 2^81865367531 is an apocalyptic number.

81865367531 is a deficient number, since it is larger than the sum of its proper divisors (1).

81865367531 is an equidigital number, since it uses as much as digits as its factorization.

81865367531 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3628800, while the sum is 53.

The spelling of 81865367531 in words is "eighty-one billion, eight hundred sixty-five million, three hundred sixty-seven thousand, five hundred thirty-one".