1649 has 4 divisors (see below), whose sum is σ = 1764.
Its totient is φ = 1536.
The previous prime is 1637. The next prime is 1657. The reversal of 1649 is 9461.
It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.
It can be written as a sum of positive squares in 2 ways, for example, as 1024 + 625 = 32^2 + 25^2
It is a cyclic number.
It is a de Polignac number, because none of the positive numbers 2k-1649 is a prime.
It is a Leyland number of the form 54 + 45.
It is a Duffinian number.
It is a Curzon number.
It is a plaindrome in base 6, base 11 and base 13.
It is a nialpdrome in base 12.
It is a self number, because there is not a number n which added to its sum of digits gives 1649.
It is a congruent number.
It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 1649.
It is not an unprimeable number, because it can be changed into a prime (1609) by changing a digit.
It is an upside-down number.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 32 + ... + 65.
It is an arithmetic number, because the mean of its divisors is an integer number (441).
It is an amenable number.
1649 is a deficient number, since it is larger than the sum of its proper divisors (115).
1649 is an equidigital number, since it uses as much as digits as its factorization.
1649 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 114.
The product of its digits is 216, while the sum is 20.
The square root of 1649 is about 40.6078810085.
The cubic root of 1649 is about 11.8142698187.
It can be divided in two parts, 16 and 49, that multiplied together give a square (784 = 282).
The spelling of 1649 in words is "one thousand, six hundred forty-nine".