81310309 has 2 divisors, whose sum is σ = 81310310. Its totient is φ = 81310308.

The previous prime is 81310301. The next prime is 81310351. The reversal of 81310309 is 90301318.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 76912900 + 4397409 = 8770^2 + 2097^2 .

It is a cyclic number.

It is not a de Polignac number, because 81310309 - 2³ = 81310301 is a prime.

It is a super-2 number, since 2×81310309² = 13222732699350962, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81310301) 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 as a sum of consecutive naturals, namely, 40655154 + 40655155.

It is an arithmetic number, because the mean of its divisors is an integer number (40655155).

Almost surely, 2^81310309 is an apocalyptic number.

It is an amenable number.

81310309 is a deficient number, since it is larger than the sum of its proper divisors (1).

81310309 is an equidigital number, since it uses as much as digits as its factorization.

81310309 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 648, while the sum is 25.

The square root of 81310309 is about 9017.2229095215. Note that the first 3 decimals coincide. The cubic root of 81310309 is about 433.2266892730.

The spelling of 81310309 in words is "eighty-one million, three hundred ten thousand, three hundred nine".