1666643321 has 12 divisors (see below), whose sum is σ = 1983838032. Its totient is φ = 1395327528.

The previous prime is 1666643299. The next prime is 1666643327. The reversal of 1666643321 is 1233466661.

It is not a de Polignac number, because 1666643321 - 2³⁰ = 592901497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1666643327) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 393395 + ... + 397608.

It is an arithmetic number, because the mean of its divisors is an integer number (165319836).

Almost surely, 2^1666643321 is an apocalyptic number.

It is an amenable number.

1666643321 is a deficient number, since it is larger than the sum of its proper divisors (317194711).

1666643321 is an equidigital number, since it uses as much as digits as its factorization.

1666643321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 791060 (or 791053 counting only the distinct ones).

The product of its digits is 93312, while the sum is 38.

The square root of 1666643321 is about 40824.5431205298. The cubic root of 1666643321 is about 1185.6255656011.

The spelling of 1666643321 in words is "one billion, six hundred sixty-six million, six hundred forty-three thousand, three hundred twenty-one".