21131210 has 16 divisors (see below), whose sum is σ = 38097000. Its totient is φ = 8438976.

The previous prime is 21131191. The next prime is 21131251. The reversal of 21131210 is 1213112.

It can be written as a sum of positive squares in 4 ways, for example, as 20511841 + 619369 = 4529^2 + 787^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21131191 and 21131200.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 7016 + ... + 9564.

Almost surely, 2^21131210 is an apocalyptic number.

21131210 is a deficient number, since it is larger than the sum of its proper divisors (16965790).

21131210 is a wasteful number, since it uses less digits than its factorization.

21131210 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3385.

The product of its (nonzero) digits is 12, while the sum is 11.

The square root of 21131210 is about 4596.8695870124. The cubic root of 21131210 is about 276.4658257552.

Adding to 21131210 its reverse (1213112), we get a palindrome (22344322).

The spelling of 21131210 in words is "twenty-one million, one hundred thirty-one thousand, two hundred ten".