21210237 has 12 divisors (see below), whose sum is σ = 32439420. Its totient is φ = 13308288.

The previous prime is 21210227. The next prime is 21210269. The reversal of 21210237 is 73201212.

It can be written as a sum of positive squares in 2 ways, for example, as 14584761 + 6625476 = 3819^2 + 2574^2 .

It is not a de Polignac number, because 21210237 - 2⁴ = 21210221 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 69162 + ... + 69467.

It is an arithmetic number, because the mean of its divisors is an integer number (2703285).

Almost surely, 2^21210237 is an apocalyptic number.

It is an amenable number.

21210237 is a deficient number, since it is larger than the sum of its proper divisors (11229183).

21210237 is a wasteful number, since it uses less digits than its factorization.

21210237 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 138652 (or 138649 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 18.

The square root of 21210237 is about 4605.4573062835. The cubic root of 21210237 is about 276.8100414917.

Adding to 21210237 its reverse (73201212), we get a palindrome (94411449).

The spelling of 21210237 in words is "twenty-one million, two hundred ten thousand, two hundred thirty-seven".