21530238 has 16 divisors (see below), whose sum is σ = 44545680. Its totient is φ = 6929216.

The previous prime is 21530237. The next prime is 21530251. The reversal of 21530238 is 83203512.

It is a super-2 number, since 2×21530238² = 927102296673288, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21530233) 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, 61695 + ... + 62042.

It is an arithmetic number, because the mean of its divisors is an integer number (2784105).

Almost surely, 2^21530238 is an apocalyptic number.

21530238 is an abundant number, since it is smaller than the sum of its proper divisors (23015442).

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

21530238 is a wasteful number, since it uses less digits than its factorization.

21530238 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 123771.

The product of its (nonzero) digits is 1440, while the sum is 24.

The square root of 21530238 is about 4640.0687494907. The cubic root of 21530238 is about 278.1951858050.

The spelling of 21530238 in words is "twenty-one million, five hundred thirty thousand, two hundred thirty-eight".