138243421 has 2 divisors, whose sum is σ = 138243422. Its totient is φ = 138243420.

The previous prime is 138243419. The next prime is 138243481. The reversal of 138243421 is 124342831.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 113103225 + 25140196 = 10635^2 + 5014^2 .

It is an emirp because it is prime and its reverse (124342831) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 138243421 - 2¹ = 138243419 is a prime.

It is a super-2 number, since 2×138243421² = 38222486899566482, which contains 22 as substring.

Together with 138243419, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 138243421.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (138243481) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69121710 + 69121711.

It is an arithmetic number, because the mean of its divisors is an integer number (69121711).

Almost surely, 2^138243421 is an apocalyptic number.

It is an amenable number.

138243421 is a deficient number, since it is larger than the sum of its proper divisors (1).

138243421 is an equidigital number, since it uses as much as digits as its factorization.

138243421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4608, while the sum is 28.

The square root of 138243421 is about 11757.6962454386. The cubic root of 138243421 is about 517.0685908046.

The spelling of 138243421 in words is "one hundred thirty-eight million, two hundred forty-three thousand, four hundred twenty-one".