21205430 has 16 divisors (see below), whose sum is σ = 38796624. Its totient is φ = 8342880.

The previous prime is 21205399. The next prime is 21205447. The reversal of 21205430 is 3450212.

It is a super-2 number, since 2×21205430² = 899340522969800, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21205399 and 21205408.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 16772 + ... + 17991.

It is an arithmetic number, because the mean of its divisors is an integer number (2424789).

Almost surely, 2^21205430 is an apocalyptic number.

21205430 is a deficient number, since it is larger than the sum of its proper divisors (17591194).

21205430 is a wasteful number, since it uses less digits than its factorization.

21205430 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34831.

The product of its (nonzero) digits is 240, while the sum is 17.

The square root of 21205430 is about 4604.9353958552. The cubic root of 21205430 is about 276.7891282191.

Adding to 21205430 its reverse (3450212), we get a palindrome (24655642).

The spelling of 21205430 in words is "twenty-one million, two hundred five thousand, four hundred thirty".