21231212213 has 2 divisors, whose sum is σ = 21231212214. Its totient is φ = 21231212212.

The previous prime is 21231212183. The next prime is 21231212227. The reversal of 21231212213 is 31221213212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21002386084 + 228826129 = 144922^2 + 15127^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21231212213 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21231232213) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10615606106 + 10615606107.

It is an arithmetic number, because the mean of its divisors is an integer number (10615606107).

Almost surely, 2^21231212213 is an apocalyptic number.

It is an amenable number.

21231212213 is a deficient number, since it is larger than the sum of its proper divisors (1).

21231212213 is an equidigital number, since it uses as much as digits as its factorization.

21231212213 is an evil number, because the sum of its binary digits is even.

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

Adding to 21231212213 its reverse (31221213212), we get a palindrome (52452425425).

Subtracting 21231212213 from its reverse (31221213212), we obtain a palindrome (9990000999).

The spelling of 21231212213 in words is "twenty-one billion, two hundred thirty-one million, two hundred twelve thousand, two hundred thirteen".