243121212021 has 4 divisors (see below), whose sum is σ = 324161616032. Its totient is φ = 162080808012.

The previous prime is 243121212011. The next prime is 243121212049. The reversal of 243121212021 is 120212121342.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 243121212021 - 2¹⁴ = 243121195637 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (243121212011) 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, 40520202001 + ... + 40520202006.

It is an arithmetic number, because the mean of its divisors is an integer number (81040404008).

Almost surely, 2^243121212021 is an apocalyptic number.

It is an amenable number.

243121212021 is a deficient number, since it is larger than the sum of its proper divisors (81040404011).

243121212021 is an equidigital number, since it uses as much as digits as its factorization.

243121212021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81040404010.

The product of its (nonzero) digits is 384, while the sum is 21.

Adding to 243121212021 its reverse (120212121342), we get a palindrome (363333333363).

The spelling of 243121212021 in words is "two hundred forty-three billion, one hundred twenty-one million, two hundred twelve thousand, twenty-one".