21205255 has 16 divisors (see below), whose sum is σ = 26468064. Its totient is φ = 16295040.

The previous prime is 21205243. The next prime is 21205279. The reversal of 21205255 is 55250212.

It is not a de Polignac number, because 21205255 - 2⁷ = 21205127 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 14665 + ... + 16045.

It is an arithmetic number, because the mean of its divisors is an integer number (1654254).

Almost surely, 2^21205255 is an apocalyptic number.

21205255 is a deficient number, since it is larger than the sum of its proper divisors (5262809).

21205255 is a wasteful number, since it uses less digits than its factorization.

21205255 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1506.

The product of its (nonzero) digits is 1000, while the sum is 22.

The square root of 21205255 is about 4604.9163944636. The cubic root of 21205255 is about 276.7883668067.

Adding to 21205255 its reverse (55250212), we get a palindrome (76455467).

The spelling of 21205255 in words is "twenty-one million, two hundred five thousand, two hundred fifty-five".