1666535609 has 2 divisors, whose sum is σ = 1666535610. Its totient is φ = 1666535608.

The previous prime is 1666535597. The next prime is 1666535621. The reversal of 1666535609 is 9065356661.

It is a balanced prime because it is at equal distance from previous prime (1666535597) and next prime (1666535621).

It can be written as a sum of positive squares in only one way, i.e., 1644708025 + 21827584 = 40555^2 + 4672^2 .

It is an emirp because it is prime and its reverse (9065356661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1666535609 - 2¹² = 1666531513 is a prime.

It is not a weakly prime, because it can be changed into another prime (1666535659) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 833267804 + 833267805.

It is an arithmetic number, because the mean of its divisors is an integer number (833267805).

Almost surely, 2^1666535609 is an apocalyptic number.

It is an amenable number.

1666535609 is a deficient number, since it is larger than the sum of its proper divisors (1).

1666535609 is an equidigital number, since it uses as much as digits as its factorization.

1666535609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 874800, while the sum is 47.

The square root of 1666535609 is about 40823.2238927795. The cubic root of 1666535609 is about 1185.6000234729.

The spelling of 1666535609 in words is "one billion, six hundred sixty-six million, five hundred thirty-five thousand, six hundred nine".