1666739209 has 2 divisors, whose sum is σ = 1666739210. Its totient is φ = 1666739208.

The previous prime is 1666739189. The next prime is 1666739219. The reversal of 1666739209 is 9029376661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1584438025 + 82301184 = 39805^2 + 9072^2 .

It is an emirp because it is prime and its reverse (9029376661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1666739209 - 2²³ = 1658350601 is a prime.

It is not a weakly prime, because it can be changed into another prime (1666739219) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 833369604 + 833369605.

It is an arithmetic number, because the mean of its divisors is an integer number (833369605).

Almost surely, 2^1666739209 is an apocalyptic number.

It is an amenable number.

1666739209 is a deficient number, since it is larger than the sum of its proper divisors (1).

1666739209 is an equidigital number, since it uses as much as digits as its factorization.

1666739209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 734832, while the sum is 49.

The square root of 1666739209 is about 40825.7174952260. The cubic root of 1666739209 is about 1185.6483029364.

The spelling of 1666739209 in words is "one billion, six hundred sixty-six million, seven hundred thirty-nine thousand, two hundred nine".