21131031121 has 4 divisors (see below), whose sum is σ = 21171590244. Its totient is φ = 21090472000.

The previous prime is 21131031091. The next prime is 21131031151. The reversal of 21131031121 is 12113013112.

It is a happy number.

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

It is an interprime number because it is at equal distance from previous prime (21131031091) and next prime (21131031151).

It can be written as a sum of positive squares in 2 ways, for example, as 7197825600 + 13933205521 = 84840^2 + 118039^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21131031121 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21131031095 and 21131031104.

It is not an unprimeable number, because it can be changed into a prime (21131031151) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 20278780 + ... + 20279821.

It is an arithmetic number, because the mean of its divisors is an integer number (5292897561).

Almost surely, 2^21131031121 is an apocalyptic number.

It is an amenable number.

21131031121 is a deficient number, since it is larger than the sum of its proper divisors (40559123).

21131031121 is an equidigital number, since it uses as much as digits as its factorization.

21131031121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40559122.

The product of its (nonzero) digits is 36, while the sum is 16.

Adding to 21131031121 its reverse (12113013112), we get a palindrome (33244044233).

The spelling of 21131031121 in words is "twenty-one billion, one hundred thirty-one million, thirty-one thousand, one hundred twenty-one".