21205256 has 16 divisors (see below), whose sum is σ = 42098940. Its totient is φ = 9978880.

The previous prime is 21205243. The next prime is 21205279. The reversal of 21205256 is 65250212.

It can be written as a sum of positive squares in 2 ways, for example, as 20884900 + 320356 = 4570^2 + 566^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 77825 + ... + 78096.

Almost surely, 2^21205256 is an apocalyptic number.

It is an amenable number.

21205256 is a deficient number, since it is larger than the sum of its proper divisors (20893684).

21205256 is a wasteful number, since it uses less digits than its factorization.

21205256 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 155944 (or 155940 counting only the distinct ones).

The product of its (nonzero) digits is 1200, while the sum is 23.

The square root of 21205256 is about 4604.9165030432. The cubic root of 21205256 is about 276.7883711577.

Adding to 21205256 its reverse (65250212), we get a palindrome (86455468).

The spelling of 21205256 in words is "twenty-one million, two hundred five thousand, two hundred fifty-six".