21205252 has 6 divisors (see below), whose sum is σ = 37109198. Its totient is φ = 10602624.

The previous prime is 21205243. The next prime is 21205279. The reversal of 21205252 is 25250212.

It can be written as a sum of positive squares in only one way, i.e., 19061956 + 2143296 = 4366^2 + 1464^2 .

It is a super-3 number, since 3×21205252³ (a number of 23 digits) contains 333 as substring.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2650653 + ... + 2650660.

Almost surely, 2^21205252 is an apocalyptic number.

It is an amenable number.

21205252 is a deficient number, since it is larger than the sum of its proper divisors (15903946).

21205252 is a wasteful number, since it uses less digits than its factorization.

21205252 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5301317 (or 5301315 counting only the distinct ones).

The product of its (nonzero) digits is 400, while the sum is 19.

The square root of 21205252 is about 4604.9160687248. The cubic root of 21205252 is about 276.7883537539.

Adding to 21205252 its reverse (25250212), we get a palindrome (46455464).

The spelling of 21205252 in words is "twenty-one million, two hundred five thousand, two hundred fifty-two".