6690721 has 2 divisors, whose sum is σ = 6690722. Its totient is φ = 6690720.

The previous prime is 6690703. The next prime is 6690737. The reversal of 6690721 is 1270966.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 6451600 + 239121 = 2540^2 + 489^2 .

It is a cyclic number.

It is not a de Polignac number, because 6690721 - 2⁵ = 6690689 is a prime.

It is not a weakly prime, because it can be changed into another prime (6690701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3345360 + 3345361.

It is an arithmetic number, because the mean of its divisors is an integer number (3345361).

Almost surely, 2^6690721 is an apocalyptic number.

It is an amenable number.

6690721 is a deficient number, since it is larger than the sum of its proper divisors (1).

6690721 is an equidigital number, since it uses as much as digits as its factorization.

6690721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4536, while the sum is 31.

The square root of 6690721 is about 2586.6428048728. The cubic root of 6690721 is about 188.4332940169.

The spelling of 6690721 in words is "six million, six hundred ninety thousand, seven hundred twenty-one".