21724430 has 32 divisors (see below), whose sum is σ = 48129984. Its totient is φ = 6875136.

The previous prime is 21724427. The next prime is 21724433. The reversal of 21724430 is 3442712.

It is an interprime number because it is at equal distance from previous prime (21724427) and next prime (21724433).

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21724396 and 21724405.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21724433) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11027 + ... + 12846.

It is an arithmetic number, because the mean of its divisors is an integer number (1504062).

Almost surely, 2^21724430 is an apocalyptic number.

21724430 is an abundant number, since it is smaller than the sum of its proper divisors (26405554).

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

21724430 is a wasteful number, since it uses less digits than its factorization.

21724430 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23900.

The product of its (nonzero) digits is 1344, while the sum is 23.

The square root of 21724430 is about 4660.9473286018. The cubic root of 21724430 is about 279.0290776167.

The spelling of 21724430 in words is "twenty-one million, seven hundred twenty-four thousand, four hundred thirty".