6378721 has 2 divisors, whose sum is σ = 6378722. Its totient is φ = 6378720.

The previous prime is 6378703. The next prime is 6378731. The reversal of 6378721 is 1278736.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 4161600 + 2217121 = 2040^2 + 1489^2 .

It is a cyclic number.

It is not a de Polignac number, because 6378721 - 2⁹ = 6378209 is a prime.

It is not a weakly prime, because it can be changed into another prime (6378731) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3189360 + 3189361.

It is an arithmetic number, because the mean of its divisors is an integer number (3189361).

Almost surely, 2^6378721 is an apocalyptic number.

It is an amenable number.

6378721 is a deficient number, since it is larger than the sum of its proper divisors (1).

6378721 is an equidigital number, since it uses as much as digits as its factorization.

6378721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 14112, while the sum is 34.

The square root of 6378721 is about 2525.6129948985. The cubic root of 6378721 is about 185.4575574392.

The spelling of 6378721 in words is "six million, three hundred seventy-eight thousand, seven hundred twenty-one".