81749831 has 2 divisors, whose sum is σ = 81749832. Its totient is φ = 81749830.

The previous prime is 81749813. The next prime is 81749839. The reversal of 81749831 is 13894718.

Together with previous prime (81749813) 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 not a de Polignac number, because 81749831 - 2¹⁸ = 81487687 is a prime.

It is a super-2 number, since 2×81749831² = 13366069737057122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81749839) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40874915 + 40874916.

It is an arithmetic number, because the mean of its divisors is an integer number (40874916).

Almost surely, 2^81749831 is an apocalyptic number.

81749831 is a deficient number, since it is larger than the sum of its proper divisors (1).

81749831 is an equidigital number, since it uses as much as digits as its factorization.

81749831 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 48384, while the sum is 41.

The square root of 81749831 is about 9041.5613142864. The cubic root of 81749831 is about 434.0058877071.

The spelling of 81749831 in words is "eighty-one million, seven hundred forty-nine thousand, eight hundred thirty-one".