21423191 has 4 divisors (see below), whose sum is σ = 21504912. Its totient is φ = 21341472.

The previous prime is 21423169. The next prime is 21423221. The reversal of 21423191 is 19132412.

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 21423191 - 2¹⁴ = 21406807 is a prime.

It is a super-2 number, since 2×21423191² = 917906225244962, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21423161) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 40466 + ... + 40991.

It is an arithmetic number, because the mean of its divisors is an integer number (5376228).

Almost surely, 2^21423191 is an apocalyptic number.

21423191 is a deficient number, since it is larger than the sum of its proper divisors (81721).

21423191 is an equidigital number, since it uses as much as digits as its factorization.

21423191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 81720.

The product of its digits is 432, while the sum is 23.

The square root of 21423191 is about 4628.5193096713. The cubic root of 21423191 is about 277.7333632040.

The spelling of 21423191 in words is "twenty-one million, four hundred twenty-three thousand, one hundred ninety-one".