6666721739 has 2 divisors, whose sum is σ = 6666721740. Its totient is φ = 6666721738.

The previous prime is 6666721693. The next prime is 6666721807. The reversal of 6666721739 is 9371276666.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 6666721739 - 2¹² = 6666717643 is a prime.

It is not a weakly prime, because it can be changed into another prime (6666721939) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3333360869 + 3333360870.

It is an arithmetic number, because the mean of its divisors is an integer number (3333360870).

Almost surely, 2^6666721739 is an apocalyptic number.

6666721739 is a deficient number, since it is larger than the sum of its proper divisors (1).

6666721739 is an equidigital number, since it uses as much as digits as its factorization.

6666721739 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3429216, while the sum is 53.

The square root of 6666721739 is about 81649.9953398651. The cubic root of 6666721739 is about 1882.0772402528.

The spelling of 6666721739 in words is "six billion, six hundred sixty-six million, seven hundred twenty-one thousand, seven hundred thirty-nine".