21204550 has 12 divisors (see below), whose sum is σ = 39440556. Its totient is φ = 8481800.

The previous prime is 21204509. The next prime is 21204553. The reversal of 21204550 is 5540212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21204553) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 211996 + ... + 212095.

It is an arithmetic number, because the mean of its divisors is an integer number (3286713).

Almost surely, 2^21204550 is an apocalyptic number.

21204550 is a deficient number, since it is larger than the sum of its proper divisors (18236006).

21204550 is a wasteful number, since it uses less digits than its factorization.

21204550 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 424103 (or 424098 counting only the distinct ones).

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

The square root of 21204550 is about 4604.8398452063. The cubic root of 21204550 is about 276.7852993602.

Adding to 21204550 its reverse (5540212), we get a palindrome (26744762).

It can be divided in two parts, 2120 and 4550, that added together give a triangular number (6670 = T₁₁₅).

The spelling of 21204550 in words is "twenty-one million, two hundred four thousand, five hundred fifty".