1666378299 has 8 divisors (see below), whose sum is σ = 2338776640. Its totient is φ = 1052449416.

The previous prime is 1666378291. The next prime is 1666378333. The reversal of 1666378299 is 9928736661.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1666378299 - 2³ = 1666378291 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (57), and also a Moran number because the ratio is a prime number: 29234707 = 1666378299 / (1 + 6 + 6 + 6 + 3 + 7 + 8 + 2 + 9 + 9).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1666378291) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 14617297 + ... + 14617410.

It is an arithmetic number, because the mean of its divisors is an integer number (292347080).

Almost surely, 2^1666378299 is an apocalyptic number.

1666378299 is a gapful number since it is divisible by the number (19) formed by its first and last digit.

1666378299 is a deficient number, since it is larger than the sum of its proper divisors (672398341).

1666378299 is a wasteful number, since it uses less digits than its factorization.

1666378299 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29234729.

The product of its digits is 5878656, while the sum is 57.

The square root of 1666378299 is about 40821.2971253977. The cubic root of 1666378299 is about 1185.5627180178.

It can be divided in two parts, 166637 and 8299, that added together give a triangular number (174936 = T₅₉₁).

The spelling of 1666378299 in words is "one billion, six hundred sixty-six million, three hundred seventy-eight thousand, two hundred ninety-nine".