21531123113 has 4 divisors (see below), whose sum is σ = 21531862020. Its totient is φ = 21530384208.

The previous prime is 21531123079. The next prime is 21531123121. The reversal of 21531123113 is 31132113512.

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

It can be written as a sum of positive squares in 2 ways, for example, as 17444333929 + 4086789184 = 132077^2 + 63928^2 .

It is a cyclic number.

It is not a de Polignac number, because 21531123113 - 2⁶ = 21531123049 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21531120113) 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, 323870 + ... + 384647.

It is an arithmetic number, because the mean of its divisors is an integer number (5382965505).

Almost surely, 2^21531123113 is an apocalyptic number.

It is an amenable number.

21531123113 is a deficient number, since it is larger than the sum of its proper divisors (738907).

21531123113 is an equidigital number, since it uses as much as digits as its factorization.

21531123113 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 738906.

The product of its digits is 540, while the sum is 23.

Adding to 21531123113 its reverse (31132113512), we get a palindrome (52663236625).

The spelling of 21531123113 in words is "twenty-one billion, five hundred thirty-one million, one hundred twenty-three thousand, one hundred thirteen".