6640649 has 8 divisors (see below), whose sum is σ = 6891528. Its totient is φ = 6393600.

The previous prime is 6640639. The next prime is 6640651. The reversal of 6640649 is 9460466.

It can be written as a sum of positive squares in 4 ways, for example, as 4182025 + 2458624 = 2045^2 + 1568^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 6640649 - 2⁸ = 6640393 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6640639) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2849 + ... + 4625.

It is an arithmetic number, because the mean of its divisors is an integer number (861441).

Almost surely, 2^6640649 is an apocalyptic number.

It is an amenable number.

6640649 is a deficient number, since it is larger than the sum of its proper divisors (250879).

6640649 is a wasteful number, since it uses less digits than its factorization.

6640649 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1915.

The product of its (nonzero) digits is 31104, while the sum is 35.

The square root of 6640649 is about 2576.9456726908. The cubic root of 6640649 is about 187.9620509641.

The spelling of 6640649 in words is "six million, six hundred forty thousand, six hundred forty-nine".