81091039 has 4 divisors (see below), whose sum is σ = 81109080. Its totient is φ = 81073000.

The previous prime is 81091019. The next prime is 81091061. The reversal of 81091039 is 93019018.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 81091039 - 2¹⁹ = 80566751 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81091039.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81091019) 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 in 3 ways as a sum of consecutive naturals, for example, 3732 + ... + 13270.

It is an arithmetic number, because the mean of its divisors is an integer number (20277270).

Almost surely, 2^81091039 is an apocalyptic number.

81091039 is a deficient number, since it is larger than the sum of its proper divisors (18041).

81091039 is an equidigital number, since it uses as much as digits as its factorization.

81091039 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18040.

The product of its (nonzero) digits is 1944, while the sum is 31.

The square root of 81091039 is about 9005.0563018784. The cubic root of 81091039 is about 432.8369103489.

The spelling of 81091039 in words is "eighty-one million, ninety-one thousand, thirty-nine".