21205522 has 16 divisors (see below), whose sum is σ = 34335000.
Its totient is φ = 9764352.
The previous prime is 21205453. The next prime is 21205523. The reversal of 21205522 is 22550212.
It can be written as a sum of positive squares in 4 ways, for example, as 10830681 + 10374841 = 3291^2 + 3221^2
It is a self number, because there is not a number n which added to its sum of digits gives 21205522.
It is not an unprimeable number, because it can be changed into a prime (21205523) by changing a digit.
It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 16354 + ... + 17602.
Almost surely, 221205522 is an apocalyptic number.
21205522 is a deficient number, since it is larger than the sum of its proper divisors (13129478).
21205522 is a wasteful number, since it uses less digits than its factorization.
21205522 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 1917.
The product of its (nonzero) digits is 400, while the sum is 19.
The square root of 21205522 is about 4604.9453851267.
The cubic root of 21205522 is about 276.7895285028.
Adding to 21205522 its reverse (22550212), we get a palindrome (43755734).
The spelling of 21205522 in words is "twenty-one million, two hundred five thousand, five hundred twenty-two".