1689 has 4 divisors (see below), whose sum is σ = 2256. Its totient is φ = 1124.

The previous prime is 1669. The next prime is 1693. The reversal of 1689 is 9861.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1689 - 2⁵ = 1657 is a prime.

It is a D-number.

It is a plaindrome in base 10, base 13, base 14, base 15 and base 16.

It is not an unprimeable number, because it can be changed into a prime (1609) 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, 279 + ... + 284.

It is an arithmetic number, because the mean of its divisors is an integer number (564).

It is an amenable number.

1689 is a deficient number, since it is larger than the sum of its proper divisors (567).

1689 is an equidigital number, since it uses as much as digits as its factorization.

1689 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 566.

The product of its digits is 432, while the sum is 24.

The square root of 1689 is about 41.0974451761. The cubic root of 1689 is about 11.9090344030.

It can be divided in two parts, 16 and 89, that added together give a triangular number (105 = T₁₄).

The spelling of 1689 in words is "one thousand, six hundred eighty-nine".