138221861 has 2 divisors, whose sum is σ = 138221862. Its totient is φ = 138221860.

The previous prime is 138221857. The next prime is 138221879. The reversal of 138221861 is 168122831.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 93412225 + 44809636 = 9665^2 + 6694^2 .

It is a cyclic number.

It is not a de Polignac number, because 138221861 - 2² = 138221857 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (138221761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69110930 + 69110931.

It is an arithmetic number, because the mean of its divisors is an integer number (69110931).

Almost surely, 2^138221861 is an apocalyptic number.

It is an amenable number.

138221861 is a deficient number, since it is larger than the sum of its proper divisors (1).

138221861 is an equidigital number, since it uses as much as digits as its factorization.

138221861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4608, while the sum is 32.

The square root of 138221861 is about 11756.7793634141. The cubic root of 138221861 is about 517.0417092881.

The spelling of 138221861 in words is "one hundred thirty-eight million, two hundred twenty-one thousand, eight hundred sixty-one".