21158223 has 4 divisors (see below), whose sum is σ = 28210968. Its totient is φ = 14105480.

The previous prime is 21158201. The next prime is 21158231. The reversal of 21158223 is 32285112.

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 21158223 - 2¹⁸ = 20896079 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21158193 and 21158202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21158273) 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, 3526368 + ... + 3526373.

It is an arithmetic number, because the mean of its divisors is an integer number (7052742).

Almost surely, 2^21158223 is an apocalyptic number.

21158223 is a deficient number, since it is larger than the sum of its proper divisors (7052745).

21158223 is an equidigital number, since it uses as much as digits as its factorization.

21158223 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7052744.

The product of its digits is 960, while the sum is 24.

The square root of 21158223 is about 4599.8068437707. The cubic root of 21158223 is about 276.5835819289.

The spelling of 21158223 in words is "twenty-one million, one hundred fifty-eight thousand, two hundred twenty-three".