• 280 can be written using four 4's:

280 has 16 divisors (see below), whose sum is σ = 720. Its totient is φ = 96.

The previous prime is 277. The next prime is 281. The reversal of 280 is 82.

280 = T_{8} + T_{9} + ... +
T_{12}.

280 = 3^{2} + 4^{2} + ... + 9^{2}.

It is a happy number.

280 is nontrivially palindromic in base 3.

It is a Harshad number since it is a multiple of its sum of digits (10).

It is a super Niven number, because it is divisible the sum of any subset of its (nonzero) digits.

280 is an idoneal number.

It is a plaindrome in base 6, base 11, base 15 and base 16.

It is a nialpdrome in base 5, base 7 and base 8.

It is a zygodrome in base 6.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (281) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (3) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 37 + ... + 43.

It is an arithmetic number, because the mean of its divisors is an integer number (45).

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

280 is the 10-th octagonal number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (360).

280 is an abundant number, since it is smaller than the sum of its proper divisors (440).

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

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

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

The sum of its prime factors is 18 (or 14 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 10.

The square root of 280 is about 16.7332005307. The cubic root of 280 is about 6.5421326204.

280 divided by its sum of digits (10) gives a triangular number (28 = T_{7}).

The spelling of 280 in words is "two hundred eighty", and thus it is an aban number.

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