171985905 has 48 divisors (see below), whose sum is σ = 366912000. Its totient is φ = 72572544.

The previous prime is 171985903. The next prime is 171985937. The reversal of 171985905 is 509589171.

It is not a de Polignac number, because 171985905 - 2¹ = 171985903 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (171985903) 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, 16905 + ... + 25094.

It is an arithmetic number, because the mean of its divisors is an integer number (7644000).

Almost surely, 2^171985905 is an apocalyptic number.

171985905 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

171985905 is an abundant number, since it is smaller than the sum of its proper divisors (194926095).

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

171985905 is a wasteful number, since it uses less digits than its factorization.

171985905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42030 (or 42027 counting only the distinct ones).

The product of its (nonzero) digits is 113400, while the sum is 45.

The square root of 171985905 is about 13114.3396707574. The cubic root of 171985905 is about 556.1145850565.

The spelling of 171985905 in words is "one hundred seventy-one million, nine hundred eighty-five thousand, nine hundred five".