21223665 has 48 divisors (see below), whose sum is σ = 39262080. Its totient is φ = 10575360.

The previous prime is 21223663. The next prime is 21223673. The reversal of 21223665 is 56632212.

It is not a de Polignac number, because 21223665 - 2¹ = 21223663 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21223661) 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 47 ways as a sum of consecutive naturals, for example, 87945 + ... + 88185.

It is an arithmetic number, because the mean of its divisors is an integer number (817960).

Almost surely, 2^21223665 is an apocalyptic number.

It is an amenable number.

21223665 is a deficient number, since it is larger than the sum of its proper divisors (18038415).

21223665 is a wasteful number, since it uses less digits than its factorization.

21223665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 374 (or 371 counting only the distinct ones).

The product of its digits is 4320, while the sum is 27.

The square root of 21223665 is about 4606.9149113045. The cubic root of 21223665 is about 276.8684444398.

Adding to 21223665 its reverse (56632212), we get a palindrome (77855877).

The spelling of 21223665 in words is "twenty-one million, two hundred twenty-three thousand, six hundred sixty-five".