21642223 has 4 divisors (see below), whose sum is σ = 21752280. Its totient is φ = 21532168.

The previous prime is 21642217. The next prime is 21642233. The reversal of 21642223 is 32224612.

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 21642223 - 2⁵ = 21642191 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21642194 and 21642203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21642233) 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, 54733 + ... + 55126.

It is an arithmetic number, because the mean of its divisors is an integer number (5438070).

Almost surely, 2^21642223 is an apocalyptic number.

21642223 is a deficient number, since it is larger than the sum of its proper divisors (110057).

21642223 is a wasteful number, since it uses less digits than its factorization.

21642223 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 110056.

The product of its digits is 1152, while the sum is 22.

The square root of 21642223 is about 4652.1202692966. The cubic root of 21642223 is about 278.6766765391.

Adding to 21642223 its reverse (32224612), we get a palindrome (53866835).

The spelling of 21642223 in words is "twenty-one million, six hundred forty-two thousand, two hundred twenty-three".