21305430 has 80 divisors (see below), whose sum is σ = 59328720. Its totient is φ = 5479488.

The previous prime is 21305423. The next prime is 21305461. The reversal of 21305430 is 3450312.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 23037 + ... + 23943.

It is an arithmetic number, because the mean of its divisors is an integer number (741609).

Almost surely, 2^21305430 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21305430, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29664360).

21305430 is an abundant number, since it is smaller than the sum of its proper divisors (38023290).

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

21305430 is a wasteful number, since it uses less digits than its factorization.

21305430 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 955 (or 946 counting only the distinct ones).

The product of its (nonzero) digits is 360, while the sum is 18.

The square root of 21305430 is about 4615.7805407103. The cubic root of 21305430 is about 277.2235376651.

Adding to 21305430 its reverse (3450312), we get a palindrome (24755742).

The spelling of 21305430 in words is "twenty-one million, three hundred five thousand, four hundred thirty".