21205434 has 16 divisors (see below), whose sum is σ = 42823872. Its totient is φ = 6999648.

The previous prime is 21205399. The next prime is 21205447. The reversal of 21205434 is 43450212.

It is a super-2 number, since 2×21205434² = 899340862256712, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21205434.

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, 16539 + ... + 17774.

It is an arithmetic number, because the mean of its divisors is an integer number (2676492).

Almost surely, 2^21205434 is an apocalyptic number.

21205434 is an abundant number, since it is smaller than the sum of its proper divisors (21618438).

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

21205434 is a wasteful number, since it uses less digits than its factorization.

21205434 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34421.

The product of its (nonzero) digits is 960, while the sum is 21.

The square root of 21205434 is about 4604.9358301718. The cubic root of 21205434 is about 276.7891456228.

Adding to 21205434 its reverse (43450212), we get a palindrome (64655646).

The spelling of 21205434 in words is "twenty-one million, two hundred five thousand, four hundred thirty-four".