81809235 has 24 divisors (see below), whose sum is σ = 144132144. Its totient is φ = 42914880.

The previous prime is 81809201. The next prime is 81809237. The reversal of 81809235 is 53290818.

It is not a de Polignac number, because 81809235 - 2¹⁰ = 81808211 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81809235.

It is not an unprimeable number, because it can be changed into a prime (81809237) 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 23 ways as a sum of consecutive naturals, for example, 12157 + ... + 17646.

It is an arithmetic number, because the mean of its divisors is an integer number (6005506).

Almost surely, 2^81809235 is an apocalyptic number.

81809235 is a deficient number, since it is larger than the sum of its proper divisors (62322909).

81809235 is a wasteful number, since it uses less digits than its factorization.

81809235 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29875 (or 29872 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 36.

The square root of 81809235 is about 9044.8457698294. The cubic root of 81809235 is about 434.1109865725.

The spelling of 81809235 in words is "eighty-one million, eight hundred nine thousand, two hundred thirty-five".