21312003121 has 4 divisors (see below), whose sum is σ = 21347943012. Its totient is φ = 21276063232.

The previous prime is 21312003019. The next prime is 21312003149. The reversal of 21312003121 is 12130021312.

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 12003612721 + 9308390400 = 109561^2 + 96480^2 .

It is a cyclic number.

It is not a de Polignac number, because 21312003121 - 2¹³ = 21311994929 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21312003095 and 21312003104.

It is not an unprimeable number, because it can be changed into a prime (21312003221) 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, 17969056 + ... + 17970241.

It is an arithmetic number, because the mean of its divisors is an integer number (5336985753).

Almost surely, 2^21312003121 is an apocalyptic number.

It is an amenable number.

21312003121 is a deficient number, since it is larger than the sum of its proper divisors (35939891).

21312003121 is an equidigital number, since it uses as much as digits as its factorization.

21312003121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35939890.

The product of its (nonzero) digits is 72, while the sum is 16.

Adding to 21312003121 its reverse (12130021312), we get a palindrome (33442024433).

The spelling of 21312003121 in words is "twenty-one billion, three hundred twelve million, three thousand, one hundred twenty-one".