279840 has 96 divisors (see below), whose sum is σ = 979776. Its totient is φ = 66560.

The previous prime is 279823. The next prime is 279847. The reversal of 279840 is 48972.

It is a Cunningham number, because it is equal to 23⁴-1.

It is a tau number, because it is divible by the number of its divisors (96).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a nialpdrome in base 6.

It is a junction number, because it is equal to n+sod(n) for n = 279798 and 279807.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (279847) by changing a digit.

279840 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5254 + ... + 5306.

It is an arithmetic number, because the mean of its divisors is an integer number (10206).

279840 is a Friedman number, since it can be written as (9+7*2)^4-8^0, using all its digits and the basic arithmetic operations.

2²⁷⁹⁸⁴⁰ is an apocalyptic number.

279840 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 279840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (489888).

279840 is an abundant number, since it is smaller than the sum of its proper divisors (699936).

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

279840 is a wasteful number, since it uses less digits than its factorization.

279840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 82 (or 74 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 30.

The square root of 279840 is about 528.9990548196. Note that the first 3 decimals coincide. The cubic root of 279840 is about 65.4088626245.

The spelling of 279840 in words is "two hundred seventy-nine thousand, eight hundred forty".