81905575 has 24 divisors (see below), whose sum is σ = 108207360. Its totient is φ = 61286400.

The previous prime is 81905573. The next prime is 81905591. The reversal of 81905575 is 57550918.

It is not a de Polignac number, because 81905575 - 2¹ = 81905573 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81905573) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 80671 + ... + 81679.

It is an arithmetic number, because the mean of its divisors is an integer number (4508640).

Almost surely, 2^81905575 is an apocalyptic number.

81905575 is a gapful number since it is divisible by the number (85) formed by its first and last digit.

81905575 is a deficient number, since it is larger than the sum of its proper divisors (26301785).

81905575 is a wasteful number, since it uses less digits than its factorization.

81905575 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1227 (or 1222 counting only the distinct ones).

The product of its (nonzero) digits is 63000, while the sum is 40.

The square root of 81905575 is about 9050.1698879082. The cubic root of 81905575 is about 434.2813253137.

The spelling of 81905575 in words is "eighty-one million, nine hundred five thousand, five hundred seventy-five".