21530424 has 16 divisors (see below), whose sum is σ = 53826120. Its totient is φ = 7176800.

The previous prime is 21530413. The next prime is 21530447. The reversal of 21530424 is 42403512.

It is a self number, because there is not a number n which added to its sum of digits gives 21530424.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 448527 + ... + 448574.

Almost surely, 2^21530424 is an apocalyptic number.

21530424 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21530424 is an abundant number, since it is smaller than the sum of its proper divisors (32295696).

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

21530424 is a wasteful number, since it uses less digits than its factorization.

21530424 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 897110 (or 897106 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 21.

The square root of 21530424 is about 4640.0887922539. The cubic root of 21530424 is about 278.1959869132.

Adding to 21530424 its reverse (42403512), we get a palindrome (63933936).

It can be divided in two parts, 2153042 and 4, that multiplied together give a palindrome (8612168).

The spelling of 21530424 in words is "twenty-one million, five hundred thirty thousand, four hundred twenty-four".