243121020509 has 2 divisors, whose sum is σ = 243121020510. Its totient is φ = 243121020508.

The previous prime is 243121020491. The next prime is 243121020511. The reversal of 243121020509 is 905020121342.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 194257918009 + 48863102500 = 440747^2 + 221050^2 .

It is a cyclic number.

It is not a de Polignac number, because 243121020509 - 2²⁴ = 243104243293 is a prime.

It is a super-2 number, since 2×243121020509² (a number of 24 digits) contains 22 as substring.

Together with 243121020511, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (243121020809) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 121560510254 + 121560510255.

It is an arithmetic number, because the mean of its divisors is an integer number (121560510255).

Almost surely, 2^243121020509 is an apocalyptic number.

It is an amenable number.

243121020509 is a deficient number, since it is larger than the sum of its proper divisors (1).

243121020509 is an equidigital number, since it uses as much as digits as its factorization.

243121020509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4320, while the sum is 29.

The spelling of 243121020509 in words is "two hundred forty-three billion, one hundred twenty-one million, twenty thousand, five hundred nine".