21042191 has 4 divisors (see below), whose sum is σ = 21095592. Its totient is φ = 20988792.

The previous prime is 21042187. The next prime is 21042193. The reversal of 21042191 is 19124012.

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 21042191 - 2² = 21042187 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 (21042193) 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, 26105 + ... + 26898.

It is an arithmetic number, because the mean of its divisors is an integer number (5273898).

Almost surely, 2^21042191 is an apocalyptic number.

21042191 is a deficient number, since it is larger than the sum of its proper divisors (53401).

21042191 is an equidigital number, since it uses as much as digits as its factorization.

21042191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 53400.

The product of its (nonzero) digits is 144, while the sum is 20.

The square root of 21042191 is about 4587.1768006040. The cubic root of 21042191 is about 276.0770587536.

The spelling of 21042191 in words is "twenty-one million, forty-two thousand, one hundred ninety-one".