21123121213 has 2 divisors, whose sum is σ = 21123121214. Its totient is φ = 21123121212.

The previous prime is 21123121147. The next prime is 21123121219. The reversal of 21123121213 is 31212132112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21090881529 + 32239684 = 145227^2 + 5678^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21123121213 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21123121219) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10561560606 + 10561560607.

It is an arithmetic number, because the mean of its divisors is an integer number (10561560607).

Almost surely, 2^21123121213 is an apocalyptic number.

It is an amenable number.

21123121213 is a deficient number, since it is larger than the sum of its proper divisors (1).

21123121213 is an equidigital number, since it uses as much as digits as its factorization.

21123121213 is an odious number, because the sum of its binary digits is odd.

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

Adding to 21123121213 its reverse (31212132112), we get a palindrome (52335253325).

The spelling of 21123121213 in words is "twenty-one billion, one hundred twenty-three million, one hundred twenty-one thousand, two hundred thirteen".