1966719891 has 4 divisors (see below), whose sum is σ = 2622293192. Its totient is φ = 1311146592.

The previous prime is 1966719889. The next prime is 1966719893. The reversal of 1966719891 is 1989176691.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1989176691 = 3 ⋅663058897.

It is an interprime number because it is at equal distance from previous prime (1966719889) and next prime (1966719893).

It is not a de Polignac number, because 1966719891 - 2¹ = 1966719889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1966719893) 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 3 ways as a sum of consecutive naturals, for example, 327786646 + ... + 327786651.

It is an arithmetic number, because the mean of its divisors is an integer number (655573298).

Almost surely, 2^1966719891 is an apocalyptic number.

1966719891 is a deficient number, since it is larger than the sum of its proper divisors (655573301).

1966719891 is an equidigital number, since it uses as much as digits as its factorization.

1966719891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 655573300.

The product of its digits is 1469664, while the sum is 57.

The square root of 1966719891 is about 44347.7157359880. The cubic root of 1966719891 is about 1252.8935401852.

The spelling of 1966719891 in words is "one billion, nine hundred sixty-six million, seven hundred nineteen thousand, eight hundred ninety-one".