21255238 has 4 divisors (see below), whose sum is σ = 31882860. Its totient is φ = 10627618.

The previous prime is 21255217. The next prime is 21255239. The reversal of 21255238 is 83255212.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21255239) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5313808 + ... + 5313811.

It is an arithmetic number, because the mean of its divisors is an integer number (7970715).

Almost surely, 2^21255238 is an apocalyptic number.

21255238 is a deficient number, since it is larger than the sum of its proper divisors (10627622).

21255238 is a wasteful number, since it uses less digits than its factorization.

21255238 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10627621.

The product of its digits is 4800, while the sum is 28.

The square root of 21255238 is about 4610.3403345089. The cubic root of 21255238 is about 277.0056691876.

The spelling of 21255238 in words is "twenty-one million, two hundred fifty-five thousand, two hundred thirty-eight".