21691869191 has 4 divisors (see below), whose sum is σ = 21693469800. Its totient is φ = 21690268584.

The previous prime is 21691869187. The next prime is 21691869223. The reversal of 21691869191 is 19196819612.

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 21691869191 - 2² = 21691869187 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 (21691869791) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 779801 + ... + 807138.

It is an arithmetic number, because the mean of its divisors is an integer number (5423367450).

Almost surely, 2^21691869191 is an apocalyptic number.

21691869191 is a deficient number, since it is larger than the sum of its proper divisors (1600609).

21691869191 is a wasteful number, since it uses less digits than its factorization.

21691869191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1600608.

The product of its digits is 419904, while the sum is 53.

The spelling of 21691869191 in words is "twenty-one billion, six hundred ninety-one million, eight hundred sixty-nine thousand, one hundred ninety-one".