138137221 has 2 divisors, whose sum is σ = 138137222. Its totient is φ = 138137220.

The previous prime is 138137203. The next prime is 138137297. The reversal of 138137221 is 122731831.

138137221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 77686596 + 60450625 = 8814^2 + 7775^2 .

It is an emirp because it is prime and its reverse (122731831) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 138137221 - 2⁷ = 138137093 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 138137221.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (138137521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69068610 + 69068611.

It is an arithmetic number, because the mean of its divisors is an integer number (69068611).

Almost surely, 2^138137221 is an apocalyptic number.

It is an amenable number.

138137221 is a deficient number, since it is larger than the sum of its proper divisors (1).

138137221 is an equidigital number, since it uses as much as digits as its factorization.

138137221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2016, while the sum is 28.

The square root of 138137221 is about 11753.1791869264. The cubic root of 138137221 is about 516.9361511040.

The spelling of 138137221 in words is "one hundred thirty-eight million, one hundred thirty-seven thousand, two hundred twenty-one".