1991402771 has 2 divisors, whose sum is σ = 1991402772. Its totient is φ = 1991402770.

The previous prime is 1991402747. The next prime is 1991402773. The reversal of 1991402771 is 1772041991.

It is a strong prime.

It is an emirp because it is prime and its reverse (1772041991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1991402771 - 2¹⁰ = 1991401747 is a prime.

Together with 1991402773, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (1991402773) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995701385 + 995701386.

It is an arithmetic number, because the mean of its divisors is an integer number (995701386).

Almost surely, 2^1991402771 is an apocalyptic number.

1991402771 is a deficient number, since it is larger than the sum of its proper divisors (1).

1991402771 is an equidigital number, since it uses as much as digits as its factorization.

1991402771 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 31752, while the sum is 41.

The square root of 1991402771 is about 44625.1360894283. The cubic root of 1991402771 is about 1258.1131519649.

The spelling of 1991402771 in words is "one billion, nine hundred ninety-one million, four hundred two thousand, seven hundred seventy-one".