285 has 8 divisors (see below), whose sum is σ = 480. Its totient is φ = 144.

The previous prime is 283. The next prime is 293. The reversal of 285 is 582.

285 = T_{2} + T_{3} + ... +
T_{11}.

285 = 1^{2} + 2^{2} + ... + 9^{2}.

285 is nontrivially palindromic in base 7.

It is a sphenic number, since it is the product of 3 distinct primes.

285 is an anti-perfect number.

It is not a de Polignac number, because 285 - 2^{1} = 283 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (15), and also a Moran number because the ratio is a prime number: 19 = 285 / (2 + 8 + 5).

It is a Curzon number.

285 is a lucky number.

285 is a nontrivial repdigit in base 7.

It is a plaindrome in base 7, base 9, base 11, base 13 and base 16.

It is a nialpdrome in base 7.

It is a zygodrome in base 7.

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 (5) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6 + ... + 24.

It is an arithmetic number, because the mean of its divisors is an integer number (60).

2^{285} is an apocalyptic number.

It is an amenable number.

285 is a deficient number, since it is larger than the sum of its proper divisors (195).

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

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

The sum of its prime factors is 27.

The product of its digits is 80, while the sum is 15.

The square root of 285 is about 16.8819430161. The cubic root of 285 is about 6.5808443652.

Adding to 285 its sum of digits (15), we get a triangular number (300 = T_{24}).

It can be divided in two parts, 28 and 5, that added together give a palindrome (33).

The spelling of 285 in words is "two hundred eighty-five", and thus it is an aban number.

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