21447424 has 36 divisors (see below), whose sum is σ = 43128400. Its totient is φ = 10644480.

The previous prime is 21447407. The next prime is 21447427. The reversal of 21447424 is 42474412.

It is a hoax number, since the sum of its digits (28) coincides with the sum of the digits of its distinct prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 21447392 and 21447401.

It is not an unprimeable number, because it can be changed into a prime (21447427) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 50734 + ... + 51154.

Almost surely, 2^21447424 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21447424, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21564200).

21447424 is an abundant number, since it is smaller than the sum of its proper divisors (21680976).

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

21447424 is an equidigital number, since it uses as much as digits as its factorization.

21447424 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 636 (or 622 counting only the distinct ones).

The product of its digits is 7168, while the sum is 28.

The square root of 21447424 is about 4631.1363616288. The cubic root of 21447424 is about 277.8380437891.

The spelling of 21447424 in words is "twenty-one million, four hundred forty-seven thousand, four hundred twenty-four".