81371309 has 12 divisors (see below), whose sum is σ = 85611036. Its totient is φ = 77332992.

The previous prime is 81371261. The next prime is 81371317. The reversal of 81371309 is 90317318.

It can be written as a sum of positive squares in 2 ways, for example, as 29214025 + 52157284 = 5405^2 + 7222^2 .

It is not a de Polignac number, because 81371309 - 2²⁰ = 80322733 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81371359) 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 11 ways as a sum of consecutive naturals, for example, 101699 + ... + 102495.

It is an arithmetic number, because the mean of its divisors is an integer number (7134253).

Almost surely, 2^81371309 is an apocalyptic number.

It is an amenable number.

81371309 is a deficient number, since it is larger than the sum of its proper divisors (4239727).

81371309 is a wasteful number, since it uses less digits than its factorization.

81371309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1036 (or 1013 counting only the distinct ones).

The product of its (nonzero) digits is 4536, while the sum is 32.

The square root of 81371309 is about 9020.6046914827. The cubic root of 81371309 is about 433.3349995334.

The spelling of 81371309 in words is "eighty-one million, three hundred seventy-one thousand, three hundred nine".