21123191 has 8 divisors (see below), whose sum is σ = 21821184. Its totient is φ = 20434680.

The previous prime is 21123187. The next prime is 21123211. The reversal of 21123191 is 19132112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21123191 - 2² = 21123187 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 (21123161) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2306 + ... + 6896.

It is an arithmetic number, because the mean of its divisors is an integer number (2727648).

Almost surely, 2^21123191 is an apocalyptic number.

21123191 is a deficient number, since it is larger than the sum of its proper divisors (697993).

21123191 is a wasteful number, since it uses less digits than its factorization.

21123191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4741.

The product of its digits is 108, while the sum is 20.

The square root of 21123191 is about 4595.9972802429. The cubic root of 21123191 is about 276.4308496866.

The spelling of 21123191 in words is "twenty-one million, one hundred twenty-three thousand, one hundred ninety-one".