1666379521 has 2 divisors, whose sum is σ = 1666379522. Its totient is φ = 1666379520.

The previous prime is 1666379513. The next prime is 1666379531. The reversal of 1666379521 is 1259736661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1347257025 + 319122496 = 36705^2 + 17864^2 .

It is an emirp because it is prime and its reverse (1259736661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1666379521 - 2³ = 1666379513 is a prime.

It is not a weakly prime, because it can be changed into another prime (1666379531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 833189760 + 833189761.

It is an arithmetic number, because the mean of its divisors is an integer number (833189761).

Almost surely, 2^1666379521 is an apocalyptic number.

It is an amenable number.

1666379521 is a deficient number, since it is larger than the sum of its proper divisors (1).

1666379521 is an equidigital number, since it uses as much as digits as its factorization.

1666379521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 408240, while the sum is 46.

The square root of 1666379521 is about 40821.3120930722. The cubic root of 1666379521 is about 1185.5630078194.

The spelling of 1666379521 in words is "one billion, six hundred sixty-six million, three hundred seventy-nine thousand, five hundred twenty-one".