1669 has 2 divisors, whose sum is σ = 1670.
Its totient is φ = 1668.
The previous prime is 1667. The next prime is 1693. The reversal of 1669 is 9661.
It is a weak prime.
It can be written as a sum of positive squares in only one way, i.e., 1444 + 225 = 38^2 + 15^2
It is an emirp because it is prime and its reverse (9661) is a distict prime.
It is a cyclic number.
It is not a de Polignac number, because 1669 - 21 = 1667 is a prime.
It is a super-2 number, since 2×16692 = 5571122, which contains 22 as substring.
Together with 1667, it forms a pair of twin primes.
It is a Chen prime.
It is a plaindrome in base 10 and base 11.
It is a nialpdrome in base 12, base 14 and base 15.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (1663) 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 as a sum of consecutive naturals, namely, 834 + 835.
It is an arithmetic number, because the mean of its divisors is an integer number (835).
21669 is an apocalyptic number.
It is an amenable number.
1669 is a deficient number, since it is larger than the sum of its proper divisors (1).
1669 is an equidigital number, since it uses as much as digits as its factorization.
1669 is an odious number, because the sum of its binary digits is odd.
The product of its digits is 324, while the sum is 22.
The square root of 1669 is about 40.8533964316.
The cubic root of 1669 is about 11.8618413801.
The spelling of 1669 in words is "one thousand, six hundred sixty-nine".