285640 has 32 divisors (see below), whose sum is σ = 663480. Its totient is φ = 110592.

The previous prime is 285631. The next prime is 285641. The reversal of 285640 is 46582.

It can be written as a sum of positive squares in 4 ways, for example, as 248004 + 37636 = 498^2 + 194^2 .

It is an Ulam number.

It is not an unprimeable number, because it can be changed into a prime (285641) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1384 + ... + 1576.

2²⁸⁵⁶⁴⁰ is an apocalyptic number.

285640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 285640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (331740).

285640 is an abundant number, since it is smaller than the sum of its proper divisors (377840).

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

285640 is a wasteful number, since it uses less digits than its factorization.

285640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 241 (or 237 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 25.

The square root of 285640 is about 534.4529913846. The cubic root of 285640 is about 65.8576669468.

The spelling of 285640 in words is "two hundred eighty-five thousand, six hundred forty".