1666681001 has 2 divisors, whose sum is σ = 1666681002. Its totient is φ = 1666681000.

The previous prime is 1666680997. The next prime is 1666681013. The reversal of 1666681001 is 1001866661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1624170601 + 42510400 = 40301^2 + 6520^2 .

It is a cyclic number.

It is not a de Polignac number, because 1666681001 - 2² = 1666680997 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (1666681061) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 833340500 + 833340501.

It is an arithmetic number, because the mean of its divisors is an integer number (833340501).

Almost surely, 2^1666681001 is an apocalyptic number.

It is an amenable number.

1666681001 is a deficient number, since it is larger than the sum of its proper divisors (1).

1666681001 is an equidigital number, since it uses as much as digits as its factorization.

1666681001 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10368, while the sum is 35.

The square root of 1666681001 is about 40825.0046050212. The cubic root of 1666681001 is about 1185.6345005332.

The spelling of 1666681001 in words is "one billion, six hundred sixty-six million, six hundred eighty-one thousand, one".