280640 has 28 divisors (see below), whose sum is σ = 669036. Its totient is φ = 112128.

The previous prime is 280639. The next prime is 280673. The reversal of 280640 is 46082.

It can be written as a sum of positive squares in 2 ways, for example, as 173056 + 107584 = 416^2 + 328^2 .

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a d-powerful number, because it can be written as 2⁷ + 8³ + 6⁷ + 0 + 4³ + 0 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 119 + ... + 758.

2²⁸⁰⁶⁴⁰ is an apocalyptic number.

280640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

280640 is an abundant number, since it is smaller than the sum of its proper divisors (388396).

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

280640 is an equidigital number, since it uses as much as digits as its factorization.

280640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 894 (or 884 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 20.

The square root of 280640 is about 529.7546601966. The cubic root of 280640 is about 65.4711330949.

The spelling of 280640 in words is "two hundred eighty thousand, six hundred forty".