21223605 has 32 divisors (see below), whose sum is σ = 36900864. Its totient is φ = 10354176.

The previous prime is 21223603. The next prime is 21223613. The reversal of 21223605 is 50632212.

It is not a de Polignac number, because 21223605 - 2¹ = 21223603 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21223603) 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 31 ways as a sum of consecutive naturals, for example, 24337 + ... + 25193.

It is an arithmetic number, because the mean of its divisors is an integer number (1153152).

Almost surely, 2^21223605 is an apocalyptic number.

It is an amenable number.

21223605 is a deficient number, since it is larger than the sum of its proper divisors (15677259).

21223605 is a wasteful number, since it uses less digits than its factorization.

21223605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1005.

The product of its (nonzero) digits is 720, while the sum is 21.

The square root of 21223605 is about 4606.9083993498. The cubic root of 21223605 is about 276.8681835342.

Adding to 21223605 its reverse (50632212), we get a palindrome (71855817).

The spelling of 21223605 in words is "twenty-one million, two hundred twenty-three thousand, six hundred five".