81810031 has 6 divisors (see below), whose sum is σ = 82359240. Its totient is φ = 81264456.

The previous prime is 81810019. The next prime is 81810041. The reversal of 81810031 is 13001818.

81810031 = T₃₃₈ + T₃₃₉ + ... + T₈₀₈.

It is not a de Polignac number, because 81810031 - 2⁵ = 81809999 is a prime.

It is a super-2 number, since 2×81810031² = 13385762344441922, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81809984 and 81810011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81810041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 22990 + ... + 26308.

It is an arithmetic number, because the mean of its divisors is an integer number (13726540).

Almost surely, 2^81810031 is an apocalyptic number.

81810031 is a deficient number, since it is larger than the sum of its proper divisors (549209).

81810031 is an equidigital number, since it uses as much as digits as its factorization.

81810031 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3633 (or 3476 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 22.

The square root of 81810031 is about 9044.8897726838. The cubic root of 81810031 is about 434.1123945278.

Adding to 81810031 its reverse (13001818), we get a palindrome (94811849).

The spelling of 81810031 in words is "eighty-one million, eight hundred ten thousand, thirty-one".