21205600 has 72 divisors (see below), whose sum is σ = 55777680. Its totient is φ = 7825920.

The previous prime is 21205573. The next prime is 21205607. The reversal of 21205600 is 650212.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21205607) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9381 + ... + 11419.

It is an arithmetic number, because the mean of its divisors is an integer number (774690).

Almost surely, 2^21205600 is an apocalyptic number.

21205600 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21205600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27888840).

21205600 is an abundant number, since it is smaller than the sum of its proper divisors (34572080).

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

21205600 is a wasteful number, since it uses less digits than its factorization.

21205600 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2072 (or 2059 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 21205600 is about 4604.9538542748. The cubic root of 21205600 is about 276.7898678729.

Adding to 21205600 its reverse (650212), we get a palindrome (21855812).

The spelling of 21205600 in words is "twenty-one million, two hundred five thousand, six hundred".