81305790 has 16 divisors (see below), whose sum is σ = 195133968. Its totient is φ = 21681536.

The previous prime is 81305789. The next prime is 81305797. The reversal of 81305790 is 9750318.

It is a super-2 number, since 2×81305790² = 13221262975048200, which contains 22 as substring.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81305797) 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 7 ways as a sum of consecutive naturals, for example, 1355067 + ... + 1355126.

It is an arithmetic number, because the mean of its divisors is an integer number (12195873).

Almost surely, 2^81305790 is an apocalyptic number.

81305790 is an abundant number, since it is smaller than the sum of its proper divisors (113828178).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81305790 is a wasteful number, since it uses less digits than its factorization.

81305790 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2710203.

The product of its (nonzero) digits is 7560, while the sum is 33.

The square root of 81305790 is about 9016.9723300008. The cubic root of 81305790 is about 433.2186632809.

The spelling of 81305790 in words is "eighty-one million, three hundred five thousand, seven hundred ninety".