1891111121 has 4 divisors (see below), whose sum is σ = 1896379200. Its totient is φ = 1885843044.

The previous prime is 1891111111. The next prime is 1891111139. The reversal of 1891111121 is 1211111981.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1891111121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1891111111) 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, 2633501 + ... + 2634218.

It is an arithmetic number, because the mean of its divisors is an integer number (474094800).

Almost surely, 2^1891111121 is an apocalyptic number.

It is an amenable number.

1891111121 is a deficient number, since it is larger than the sum of its proper divisors (5268079).

1891111121 is an equidigital number, since it uses as much as digits as its factorization.

1891111121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5268078.

The product of its digits is 144, while the sum is 26.

The square root of 1891111121 is about 43486.9074665008. The cubic root of 1891111121 is about 1236.6278306603.

The spelling of 1891111121 in words is "one billion, eight hundred ninety-one million, one hundred eleven thousand, one hundred twenty-one".