81905259 has 4 divisors (see below), whose sum is σ = 109207016. Its totient is φ = 54603504.

The previous prime is 81905227. The next prime is 81905267. The reversal of 81905259 is 95250918.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 81905259 - 2⁵ = 81905227 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81905279) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13650874 + ... + 13650879.

It is an arithmetic number, because the mean of its divisors is an integer number (27301754).

Almost surely, 2^81905259 is an apocalyptic number.

81905259 is a deficient number, since it is larger than the sum of its proper divisors (27301757).

81905259 is a wasteful number, since it uses less digits than its factorization.

81905259 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27301756.

The product of its (nonzero) digits is 32400, while the sum is 39.

The square root of 81905259 is about 9050.1524296555. The cubic root of 81905259 is about 434.2807668125.

The spelling of 81905259 in words is "eighty-one million, nine hundred five thousand, two hundred fifty-nine".