1666843509251 has 2 divisors, whose sum is σ = 1666843509252. Its totient is φ = 1666843509250.

The previous prime is 1666843509241. The next prime is 1666843509313. The reversal of 1666843509251 is 1529053486661.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1666843509251 - 2⁶ = 1666843509187 is a prime.

It is not a weakly prime, because it can be changed into another prime (1666843509211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 833421754625 + 833421754626.

It is an arithmetic number, because the mean of its divisors is an integer number (833421754626).

Almost surely, 2^{1666843509251} is an apocalyptic number.

1666843509251 is a deficient number, since it is larger than the sum of its proper divisors (1).

1666843509251 is an equidigital number, since it uses as much as digits as its factorization.

1666843509251 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 9331200, while the sum is 56.

The spelling of 1666843509251 in words is "one trillion, six hundred sixty-six billion, eight hundred forty-three million, five hundred nine thousand, two hundred fifty-one".