1666378915 has 4 divisors (see below), whose sum is σ = 1999654704. Its totient is φ = 1333103128.

The previous prime is 1666378891. The next prime is 1666378921. The reversal of 1666378915 is 5198736661.

It is a happy number.

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 1666378915 - 2¹⁵ = 1666346147 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 166637887 + ... + 166637896.

It is an arithmetic number, because the mean of its divisors is an integer number (499913676).

Almost surely, 2^1666378915 is an apocalyptic number.

1666378915 is a deficient number, since it is larger than the sum of its proper divisors (333275789).

1666378915 is an equidigital number, since it uses as much as digits as its factorization.

1666378915 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 333275788.

The product of its digits is 1632960, while the sum is 52.

The square root of 1666378915 is about 40821.3046704781. The cubic root of 1666378915 is about 1185.5628641044.

The spelling of 1666378915 in words is "one billion, six hundred sixty-six million, three hundred seventy-eight thousand, nine hundred fifteen".