6667721 has 2 divisors, whose sum is σ = 6667722. Its totient is φ = 6667720.

The previous prime is 6667711. The next prime is 6667729. The reversal of 6667721 is 1277666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 5707321 + 960400 = 2389^2 + 980^2 .

It is a cyclic number.

It is not a de Polignac number, because 6667721 - 2⁶ = 6667657 is a prime.

It is not a weakly prime, because it can be changed into another prime (6667729) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3333860 + 3333861.

It is an arithmetic number, because the mean of its divisors is an integer number (3333861).

Almost surely, 2^6667721 is an apocalyptic number.

It is an amenable number.

6667721 is a deficient number, since it is larger than the sum of its proper divisors (1).

6667721 is an equidigital number, since it uses as much as digits as its factorization.

6667721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 21168, while the sum is 35.

The square root of 6667721 is about 2582.1930601719. The cubic root of 6667721 is about 188.2171269097.

The spelling of 6667721 in words is "six million, six hundred sixty-seven thousand, seven hundred twenty-one".