1666818331 has 4 divisors (see below), whose sum is σ = 1705581592. Its totient is φ = 1628055072.

The previous prime is 1666818313. The next prime is 1666818337. The reversal of 1666818331 is 1338186661.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1666818331 - 2¹⁹ = 1666294043 is a prime.

It is a super-2 number, since 2×1666818331² = 5556566697115251122, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (43), and also a Moran number because the ratio is a prime number: 38763217 = 1666818331 / (1 + 6 + 6 + 6 + 8 + 1 + 8 + 3 + 3 + 1).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1666818337) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19381566 + ... + 19381651.

It is an arithmetic number, because the mean of its divisors is an integer number (426395398).

Almost surely, 2^1666818331 is an apocalyptic number.

1666818331 is a deficient number, since it is larger than the sum of its proper divisors (38763261).

1666818331 is an equidigital number, since it uses as much as digits as its factorization.

1666818331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38763260.

The product of its digits is 124416, while the sum is 43.

The square root of 1666818331 is about 40826.6865052750. The cubic root of 1666818331 is about 1185.6670639960.

The spelling of 1666818331 in words is "one billion, six hundred sixty-six million, eight hundred eighteen thousand, three hundred thirty-one".