21404205 has 12 divisors (see below), whose sum is σ = 37100700. Its totient is φ = 11415552.

The previous prime is 21404183. The next prime is 21404213. The reversal of 21404205 is 50240412.

It can be written as a sum of positive squares in 2 ways, for example, as 9418761 + 11985444 = 3069^2 + 3462^2 .

It is not a de Polignac number, because 21404205 - 2¹² = 21400109 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 237780 + ... + 237869.

It is an arithmetic number, because the mean of its divisors is an integer number (3091725).

Almost surely, 2^21404205 is an apocalyptic number.

It is an amenable number.

21404205 is a deficient number, since it is larger than the sum of its proper divisors (15696495).

21404205 is a wasteful number, since it uses less digits than its factorization.

21404205 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 475660 (or 475657 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 18.

The square root of 21404205 is about 4626.4678751722. The cubic root of 21404205 is about 277.6512931999.

Adding to 21404205 its reverse (50240412), we get a palindrome (71644617).

It can be divided in two parts, 21404 and 205, that added together give a square (21609 = 147²).

The spelling of 21404205 in words is "twenty-one million, four hundred four thousand, two hundred five".