1291891 has 4 divisors (see below), whose sum is σ = 1304784. Its totient is φ = 1279000.

The previous prime is 1291883. The next prime is 1291907. The reversal of 1291891 is 1981921.

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 1291891 - 2³ = 1291883 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1291831) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6295 + ... + 6496.

It is an arithmetic number, because the mean of its divisors is an integer number (326196).

2^1291891 is an apocalyptic number.

1291891 is a deficient number, since it is larger than the sum of its proper divisors (12893).

1291891 is a wasteful number, since it uses less digits than its factorization.

1291891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12892.

The product of its digits is 1296, while the sum is 31.

The square root of 1291891 is about 1136.6138306391. The cubic root of 1291891 is about 108.9118890668.

The spelling of 1291891 in words is "one million, two hundred ninety-one thousand, eight hundred ninety-one".