81809793 has 48 divisors (see below), whose sum is σ = 132088320. Its totient is φ = 48477312.

The previous prime is 81809789. The next prime is 81809809. The reversal of 81809793 is 39790818.

It is not a de Polignac number, because 81809793 - 2² = 81809789 is a prime.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (81809743) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 489796 + ... + 489962.

It is an arithmetic number, because the mean of its divisors is an integer number (2751840).

Almost surely, 2^81809793 is an apocalyptic number.

It is an amenable number.

81809793 is a deficient number, since it is larger than the sum of its proper divisors (50278527).

81809793 is a wasteful number, since it uses less digits than its factorization.

81809793 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 318 (or 315 counting only the distinct ones).

The product of its (nonzero) digits is 108864, while the sum is 45.

The square root of 81809793 is about 9044.8766160739. The cubic root of 81809793 is about 434.1119735572. Note that the first 3 decimals are identical.

The spelling of 81809793 in words is "eighty-one million, eight hundred nine thousand, seven hundred ninety-three".