1891131287 has 4 divisors (see below), whose sum is σ = 1893733296. Its totient is φ = 1888529280.

The previous prime is 1891131283. The next prime is 1891131293. The reversal of 1891131287 is 7821311981.

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

It is a cyclic number.

It is not a de Polignac number, because 1891131287 - 2² = 1891131283 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1891131283) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1299914 + ... + 1301367.

It is an arithmetic number, because the mean of its divisors is an integer number (473433324).

Almost surely, 2^1891131287 is an apocalyptic number.

1891131287 is a deficient number, since it is larger than the sum of its proper divisors (2602009).

1891131287 is an equidigital number, since it uses as much as digits as its factorization.

1891131287 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2602008.

The product of its digits is 24192, while the sum is 41.

The square root of 1891131287 is about 43487.1393287717. The cubic root of 1891131287 is about 1236.6322262681.

The spelling of 1891131287 in words is "one billion, eight hundred ninety-one million, one hundred thirty-one thousand, two hundred eighty-seven".