6640639 has 2 divisors, whose sum is σ = 6640640. Its totient is φ = 6640638.

The previous prime is 6640631. The next prime is 6640651. The reversal of 6640639 is 9360466.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 6640639 - 2³ = 6640631 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6640631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3320319 + 3320320.

It is an arithmetic number, because the mean of its divisors is an integer number (3320320).

Almost surely, 2^6640639 is an apocalyptic number.

6640639 is a deficient number, since it is larger than the sum of its proper divisors (1).

6640639 is an equidigital number, since it uses as much as digits as its factorization.

6640639 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 23328, while the sum is 34.

The square root of 6640639 is about 2576.9437324086. The cubic root of 6640639 is about 187.9619566148.

The spelling of 6640639 in words is "six million, six hundred forty thousand, six hundred thirty-nine".