21143205 has 12 divisors (see below), whose sum is σ = 36648300. Its totient is φ = 11276352.

The previous prime is 21143203. The next prime is 21143207. The reversal of 21143205 is 50234112.

It is an interprime number because it is at equal distance from previous prime (21143203) and next prime (21143207).

It can be written as a sum of positive squares in 2 ways, for example, as 10074276 + 11068929 = 3174^2 + 3327^2 .

It is not a de Polignac number, because 21143205 - 2¹ = 21143203 is a prime.

It is a plaindrome in base 7.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21143201) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 234880 + ... + 234969.

It is an arithmetic number, because the mean of its divisors is an integer number (3054025).

Almost surely, 2^21143205 is an apocalyptic number.

It is an amenable number.

21143205 is a deficient number, since it is larger than the sum of its proper divisors (15505095).

21143205 is a wasteful number, since it uses less digits than its factorization.

21143205 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 469860 (or 469857 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21143205 is about 4598.1740941378. The cubic root of 21143205 is about 276.5181272294.

Adding to 21143205 its reverse (50234112), we get a palindrome (71377317).

The spelling of 21143205 in words is "twenty-one million, one hundred forty-three thousand, two hundred five".