21215238 has 16 divisors (see below), whose sum is σ = 46287936. Its totient is φ = 6428840.

The previous prime is 21215237. The next prime is 21215261. The reversal of 21215238 is 83251212.

It is a Smith number, since the sum of its digits (24) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21215231) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 160656 + ... + 160787.

It is an arithmetic number, because the mean of its divisors is an integer number (2892996).

Almost surely, 2^21215238 is an apocalyptic number.

21215238 is an abundant number, since it is smaller than the sum of its proper divisors (25072698).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21215238 is a wasteful number, since it uses less digits than its factorization.

21215238 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 321459.

The product of its digits is 960, while the sum is 24.

The square root of 21215238 is about 4606.0002171081. Note that the first 3 decimals coincide. The cubic root of 21215238 is about 276.8317954248.

The spelling of 21215238 in words is "twenty-one million, two hundred fifteen thousand, two hundred thirty-eight".