21542223 has 4 divisors (see below), whose sum is σ = 28722968. Its totient is φ = 14361480.

The previous prime is 21542173. The next prime is 21542231. The reversal of 21542223 is 32224512.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21542223 - 2⁶ = 21542159 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21542223.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21542233) 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, 3590368 + ... + 3590373.

It is an arithmetic number, because the mean of its divisors is an integer number (7180742).

Almost surely, 2^21542223 is an apocalyptic number.

21542223 is a deficient number, since it is larger than the sum of its proper divisors (7180745).

21542223 is an equidigital number, since it uses as much as digits as its factorization.

21542223 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7180744.

The product of its digits is 960, while the sum is 21.

The square root of 21542223 is about 4641.3600377476. The cubic root of 21542223 is about 278.2467961777.

Adding to 21542223 its reverse (32224512), we get a palindrome (53766735).

The spelling of 21542223 in words is "twenty-one million, five hundred forty-two thousand, two hundred twenty-three".