21223906 has 16 divisors (see below), whose sum is σ = 34882848. Its totient is φ = 9604800.

The previous prime is 21223901. The next prime is 21223927. The reversal of 21223906 is 60932212.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21223901) 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 7 ways as a sum of consecutive naturals, for example, 3301 + ... + 7303.

It is an arithmetic number, because the mean of its divisors is an integer number (2180178).

Almost surely, 2^21223906 is an apocalyptic number.

21223906 is a deficient number, since it is larger than the sum of its proper divisors (13658942).

21223906 is a wasteful number, since it uses less digits than its factorization.

21223906 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4257.

The product of its (nonzero) digits is 1296, while the sum is 25.

The square root of 21223906 is about 4606.9410675632. The cubic root of 21223906 is about 276.8694924059.

The spelling of 21223906 in words is "twenty-one million, two hundred twenty-three thousand, nine hundred six".