21123131213213 has 16 divisors (see below), whose sum is σ = 22430823667056. Its totient is φ = 19822687272960.

The previous prime is 21123131213203. The next prime is 21123131213227. The reversal of 21123131213213 is 31231213132112.

It can be written as a sum of positive squares in 8 ways, for example, as 53947959289 + 21069183253924 = 232267^2 + 4590118^2 .

It is a cyclic number.

It is not a de Polignac number, because 21123131213213 - 2²⁰ = 21123130164637 is a prime.

It is a super-2 number, since 2×21123131213213² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21123131213203) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 78436673 + ... + 78705513.

It is an arithmetic number, because the mean of its divisors is an integer number (1401926479191).

Almost surely, 2^{21123131213213} is an apocalyptic number.

It is an amenable number.

21123131213213 is a deficient number, since it is larger than the sum of its proper divisors (1307692453843).

21123131213213 is a wasteful number, since it uses less digits than its factorization.

21123131213213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 282304.

The product of its digits is 1296, while the sum is 26.

Adding to 21123131213213 its reverse (31231213132112), we get a palindrome (52354344345325).

The spelling of 21123131213213 in words is "twenty-one trillion, one hundred twenty-three billion, one hundred thirty-one million, two hundred thirteen thousand, two hundred thirteen".