1989 has 12 divisors (see below), whose sum is σ = 3276.
Its totient is φ = 1152.
The previous prime is 1987. The next prime is 1993. The reversal of 1989 is 9891.
1989 = T6 + T7 + ... +
1989 = 43 + 53 + ... + 93.
It can be written as a sum of positive squares in 2 ways, for example, as 900 + 1089 = 30^2 + 33^2
It is not a de Polignac number, because 1989 - 21 = 1987 is a prime.
It is a super-2 number, since 2×19892 = 7912242, which contains 22 as substring.
Its product of digits (648) is a multiple of the sum of its prime factors (36).
It is a plaindrome in base 12.
It is a nialpdrome in base 7, base 13 and base 14.
It is a zygodrome in base 12.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (1987) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (7) of ones.
It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 109 + ... + 125.
It is an arithmetic number, because the mean of its divisors is an integer number (273).
It is an amenable number.
1989 is a deficient number, since it is larger than the sum of its proper divisors (1287).
1989 is a wasteful number, since it uses less digits than its factorization.
1989 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 36 (or 33 counting only the distinct ones).
The product of its digits is 648, while the sum is 27.
The square root of 1989 is about 44.5982062420.
The cubic root of 1989 is about 12.5760694691.
Adding to 1989 its sum of digits (27), we get a triangular number (2016 = T63).
It can be divided in two parts, 1 and 989, that added together give a triangular number (990 = T44).
The spelling of 1989 in words is "one thousand, nine hundred eighty-nine".