138693221 has 2 divisors, whose sum is σ = 138693222. Its totient is φ = 138693220.

The previous prime is 138693173. The next prime is 138693251. The reversal of 138693221 is 122396831.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 138321121 + 372100 = 11761^2 + 610^2 .

It is a cyclic number.

It is not a de Polignac number, because 138693221 - 2¹⁸ = 138431077 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 (138693251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69346610 + 69346611.

It is an arithmetic number, because the mean of its divisors is an integer number (69346611).

Almost surely, 2^138693221 is an apocalyptic number.

It is an amenable number.

138693221 is a deficient number, since it is larger than the sum of its proper divisors (1).

138693221 is an equidigital number, since it uses as much as digits as its factorization.

138693221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 15552, while the sum is 35.

The square root of 138693221 is about 11776.8086084474. The cubic root of 138693221 is about 517.6287757816.

The spelling of 138693221 in words is "one hundred thirty-eight million, six hundred ninety-three thousand, two hundred twenty-one".