21210320 has 20 divisors (see below), whose sum is σ = 49314180. Its totient is φ = 8484096.

The previous prime is 21210317. The next prime is 21210337. The reversal of 21210320 is 2301212.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 12306064 + 8904256 = 3508^2 + 2984^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 132485 + ... + 132644.

It is an arithmetic number, because the mean of its divisors is an integer number (2465709).

Almost surely, 2^21210320 is an apocalyptic number.

21210320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21210320 is an abundant number, since it is smaller than the sum of its proper divisors (28103860).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21210320 is a wasteful number, since it uses less digits than its factorization.

21210320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 265142 (or 265136 counting only the distinct ones).

The product of its (nonzero) digits is 24, while the sum is 11.

The square root of 21210320 is about 4605.4663173234. The cubic root of 21210320 is about 276.8104025627.

Adding to 21210320 its reverse (2301212), we get a palindrome (23511532).

The spelling of 21210320 in words is "twenty-one million, two hundred ten thousand, three hundred twenty".