2871991781 has 4 divisors (see below), whose sum is σ = 3040932492. Its totient is φ = 2703051072.

The previous prime is 2871991753. The next prime is 2871991799. The reversal of 2871991781 is 1871991782.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1222900900 + 1649090881 = 34970^2 + 40609^2 .

It is a cyclic number.

It is not a de Polignac number, because 2871991781 - 2¹⁴ = 2871975397 is a prime.

It is a super-2 number, since 2×2871991781² = 16496673580263103922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2871991181) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 84470330 + ... + 84470363.

It is an arithmetic number, because the mean of its divisors is an integer number (760233123).

Almost surely, 2^2871991781 is an apocalyptic number.

It is an amenable number.

2871991781 is a deficient number, since it is larger than the sum of its proper divisors (168940711).

2871991781 is a wasteful number, since it uses less digits than its factorization.

2871991781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 168940710.

The product of its digits is 508032, while the sum is 53.

The square root of 2871991781 is about 53590.9673452532. The cubic root of 2871991781 is about 1421.4373762902.

Subtracting from 2871991781 its reverse (1871991782), we obtain a palindrome (999999999).

The spelling of 2871991781 in words is "two billion, eight hundred seventy-one million, nine hundred ninety-one thousand, seven hundred eighty-one".