21231321211 has 4 divisors (see below), whose sum is σ = 21231708624. Its totient is φ = 21230933800.

The previous prime is 21231321157. The next prime is 21231321217. The reversal of 21231321211 is 11212313212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21231321211 - 2¹⁵ = 21231288443 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21231321217) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 94600 + ... + 226741.

It is an arithmetic number, because the mean of its divisors is an integer number (5307927156).

Almost surely, 2^21231321211 is an apocalyptic number.

21231321211 is a deficient number, since it is larger than the sum of its proper divisors (387413).

21231321211 is an equidigital number, since it uses as much as digits as its factorization.

21231321211 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 387412.

The product of its digits is 144, while the sum is 19.

Adding to 21231321211 its reverse (11212313212), we get a palindrome (32443634423).

It can be divided in two parts, 212313212 and 11, that multiplied together give a palindrome (2335445332).

The spelling of 21231321211 in words is "twenty-one billion, two hundred thirty-one million, three hundred twenty-one thousand, two hundred eleven".