1985 has 4 divisors (see below), whose sum is σ = 2388.
Its totient is φ = 1584.
The previous prime is 1979. The next prime is 1987. The reversal of 1985 is 5891.
1985 = 312 + 322.
It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5891 = 43 ⋅137.
It can be written as a sum of positive squares in 2 ways, for example, as 1024 + 961 = 32^2 + 31^2
It is a cyclic number.
It is a de Polignac number, because none of the positive numbers 2k-1985 is a prime.
It is an Ulam number.
It is a Duffinian number.
It is a nialpdrome in base 13.
It is a self number, because there is not a number n which added to its sum of digits gives 1985.
It is not an unprimeable number, because it can be changed into a prime (1987) by changing a digit.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 194 + ... + 203.
It is an arithmetic number, because the mean of its divisors is an integer number (597).
It is a Proth number, since it is equal to 31 ⋅ 26 + 1 and 31 < 26.
1985 is the 32-nd centered square number.
It is an amenable number.
1985 is a deficient number, since it is larger than the sum of its proper divisors (403).
1985 is an equidigital number, since it uses as much as digits as its factorization.
1985 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 402.
The product of its digits is 360, while the sum is 23.
The square root of 1985 is about 44.5533388199.
The cubic root of 1985 is about 12.5676333979.
It can be divided in two parts, 198 and 5, that multiplied together give a triangular number (990 = T44).
The spelling of 1985 in words is "one thousand, nine hundred eighty-five".