21231221213 has 12 divisors (see below), whose sum is σ = 21657322560. Its totient is φ = 20813247336.

The previous prime is 21231221203. The next prime is 21231221279. The reversal of 21231221213 is 31212213212.

It is not a de Polignac number, because 21231221213 - 2²⁸ = 20962785757 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21231221203) 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, 1269218 + ... + 1285836.

It is an arithmetic number, because the mean of its divisors is an integer number (1804776880).

Almost surely, 2^21231221213 is an apocalyptic number.

It is an amenable number.

21231221213 is a deficient number, since it is larger than the sum of its proper divisors (426101347).

21231221213 is an equidigital number, since it uses as much as digits as its factorization.

21231221213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17104 (or 17045 counting only the distinct ones).

The product of its digits is 288, while the sum is 20.

Adding to 21231221213 its reverse (31212213212), we get a palindrome (52443434425).

The spelling of 21231221213 in words is "twenty-one billion, two hundred thirty-one million, two hundred twenty-one thousand, two hundred thirteen".