1991943673 has 2 divisors, whose sum is σ = 1991943674. Its totient is φ = 1991943672.

The previous prime is 1991943671. The next prime is 1991943689. The reversal of 1991943673 is 3763491991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1991569129 + 374544 = 44627^2 + 612^2 .

It is a cyclic number.

It is not a de Polignac number, because 1991943673 - 2¹ = 1991943671 is a prime.

Together with 1991943671, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 1991943673.

It is not a weakly prime, because it can be changed into another prime (1991943671) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995971836 + 995971837.

It is an arithmetic number, because the mean of its divisors is an integer number (995971837).

Almost surely, 2^1991943673 is an apocalyptic number.

It is an amenable number.

1991943673 is a deficient number, since it is larger than the sum of its proper divisors (1).

1991943673 is an equidigital number, since it uses as much as digits as its factorization.

1991943673 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1102248, while the sum is 52.

The square root of 1991943673 is about 44631.1961860759. The cubic root of 1991943673 is about 1258.2270506240.

The spelling of 1991943673 in words is "one billion, nine hundred ninety-one million, nine hundred forty-three thousand, six hundred seventy-three".