6643649 has 2 divisors, whose sum is σ = 6643650. Its totient is φ = 6643648.

The previous prime is 6643633. The next prime is 6643667. The reversal of 6643649 is 9463466.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 4840000 + 1803649 = 2200^2 + 1343^2 .

It is a cyclic number.

It is not a de Polignac number, because 6643649 - 2⁴ = 6643633 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6643699) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3321824 + 3321825.

It is an arithmetic number, because the mean of its divisors is an integer number (3321825).

Almost surely, 2^6643649 is an apocalyptic number.

It is an amenable number.

6643649 is a deficient number, since it is larger than the sum of its proper divisors (1).

6643649 is an equidigital number, since it uses as much as digits as its factorization.

6643649 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 93312, while the sum is 38.

The square root of 6643649 is about 2577.5276914128. The cubic root of 6643649 is about 187.9903514740.

The spelling of 6643649 in words is "six million, six hundred forty-three thousand, six hundred forty-nine".