2128191691 has 4 divisors (see below), whose sum is σ = 2240201800. Its totient is φ = 2016181584.

The previous prime is 2128191683. The next prime is 2128191697. The reversal of 2128191691 is 1961918212.

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 2128191691 - 2³ = 2128191683 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2128191697) 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, 56005026 + ... + 56005063.

It is an arithmetic number, because the mean of its divisors is an integer number (560050450).

Almost surely, 2^2128191691 is an apocalyptic number.

2128191691 is a deficient number, since it is larger than the sum of its proper divisors (112010109).

2128191691 is a wasteful number, since it uses less digits than its factorization.

2128191691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 112010108.

The product of its digits is 15552, while the sum is 40.

The square root of 2128191691 is about 46132.3280466096. The cubic root of 2128191691 is about 1286.2841389348.

The spelling of 2128191691 in words is "two billion, one hundred twenty-eight million, one hundred ninety-one thousand, six hundred ninety-one".