6690000721 has 2 divisors, whose sum is σ = 6690000722. Its totient is φ = 6690000720.

The previous prime is 6690000671. The next prime is 6690000739. The reversal of 6690000721 is 1270000966.

6690000721 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 3504640000 + 3185360721 = 59200^2 + 56439^2 .

It is a cyclic number.

It is not a de Polignac number, because 6690000721 - 2¹⁷ = 6689869649 is a prime.

It is a super-2 number, since 2×6690000721² = 89512219293961039682, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (6690000781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3345000360 + 3345000361.

It is an arithmetic number, because the mean of its divisors is an integer number (3345000361).

Almost surely, 2^6690000721 is an apocalyptic number.

It is an amenable number.

6690000721 is a deficient number, since it is larger than the sum of its proper divisors (1).

6690000721 is an equidigital number, since it uses as much as digits as its factorization.

6690000721 is an evil number, because the sum of its binary digits is even.

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

The square root of 6690000721 is about 81792.4245942129. The cubic root of 6690000721 is about 1884.2653194473.

The spelling of 6690000721 in words is "six billion, six hundred ninety million, seven hundred twenty-one", and thus it is an aban number.