21455424 has 63 divisors (see below), whose sum is σ = 61818393. Its totient is φ = 7114752.

The previous prime is 21455393. The next prime is 21455429. The reversal of 21455424 is 42455412.

The square root of 21455424 is 4632.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 5198400 + 16257024 = 2280^2 + 4032^2 .

It is not an unprimeable number, because it can be changed into a prime (21455429) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 111072 + ... + 111264.

Almost surely, 2^21455424 is an apocalyptic number.

21455424 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

21455424 is the 4632-nd square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21455424

21455424 is an abundant number, since it is smaller than the sum of its proper divisors (40362969).

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

21455424 is an equidigital number, since it uses as much as digits as its factorization.

21455424 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 404 (or 198 counting only the distinct ones).

The product of its digits is 6400, while the sum is 27.

The cubic root of 21455424 is about 277.8725845036.

Multiplying 21455424 by its product of digits (6400), we get a square (137314713600 = 370560²).

It can be divided in two parts, 2145 and 5424, that added together give a square (7569 = 87²).

The spelling of 21455424 in words is "twenty-one million, four hundred fifty-five thousand, four hundred twenty-four".