6390721 has 2 divisors, whose sum is σ = 6390722. Its totient is φ = 6390720.

The previous prime is 6390719. The next prime is 6390733. The reversal of 6390721 is 1270936.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 3568321 + 2822400 = 1889^2 + 1680^2 .

It is a cyclic number.

It is not a de Polignac number, because 6390721 - 2¹ = 6390719 is a prime.

Together with 6390719, it forms a pair of twin primes.

It is a Chen prime.

It is an Ulam number.

6390721 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 6390721.

It is not a weakly prime, because it can be changed into another prime (6340721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3195360 + 3195361.

It is an arithmetic number, because the mean of its divisors is an integer number (3195361).

Almost surely, 2^6390721 is an apocalyptic number.

It is an amenable number.

6390721 is a deficient number, since it is larger than the sum of its proper divisors (1).

6390721 is an equidigital number, since it uses as much as digits as its factorization.

6390721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2268, while the sum is 28.

The square root of 6390721 is about 2527.9875395263. The cubic root of 6390721 is about 185.5737822317.

The spelling of 6390721 in words is "six million, three hundred ninety thousand, seven hundred twenty-one".