6649 has 4 divisors (see below), whose sum is σ = 6820. Its totient is φ = 6480.

The previous prime is 6637. The next prime is 6653. The reversal of 6649 is 9466.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9466 = 2 ⋅4733.

It can be written as a sum of positive squares in 2 ways, for example, as 2025 + 4624 = 45^2 + 68^2 .

It is a cyclic number.

It is not a de Polignac number, because 6649 - 2⁷ = 6521 is a prime.

It is a d-powerful number, because it can be written as 6² + 4² + 6² + 9⁴ .

It is a Duffinian number.

It is a plaindrome in base 14.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6619) 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, 7 + ... + 115.

It is an arithmetic number, because the mean of its divisors is an integer number (1705).

2⁶⁶⁴⁹ is an apocalyptic number.

It is an amenable number.

6649 is a deficient number, since it is larger than the sum of its proper divisors (171).

6649 is a wasteful number, since it uses less digits than its factorization.

6649 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 170.

The product of its digits is 1296, while the sum is 25.

The square root of 6649 is about 81.5414005276. The cubic root of 6649 is about 18.8040809007.

The spelling of 6649 in words is "six thousand, six hundred forty-nine".