21131223210 has 96 divisors (see below), whose sum is σ = 58564069200. Its totient is φ = 5267871744.

The previous prime is 21131223209. The next prime is 21131223263. The reversal of 21131223210 is 1232213112.

It can be written as a sum of positive squares in 8 ways, for example, as 3394577169 + 17736646041 = 58263^2 + 133179^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 181624 + ... + 274316.

Almost surely, 2^21131223210 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21131223210, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29282034600).

21131223210 is an abundant number, since it is smaller than the sum of its proper divisors (37432845990).

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

21131223210 is a wasteful number, since it uses less digits than its factorization.

21131223210 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 92872 (or 92869 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

Adding to 21131223210 its reverse (1232213112), we get a palindrome (22363436322).

The spelling of 21131223210 in words is "twenty-one billion, one hundred thirty-one million, two hundred twenty-three thousand, two hundred ten".