138446921 has 2 divisors, whose sum is σ = 138446922. Its totient is φ = 138446920.

The previous prime is 138446851. The next prime is 138446927. The reversal of 138446921 is 129644831.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 138391696 + 55225 = 11764^2 + 235^2 .

It is an emirp because it is prime and its reverse (129644831) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 138446921 - 2²² = 134252617 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (138446927) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69223460 + 69223461.

It is an arithmetic number, because the mean of its divisors is an integer number (69223461).

Almost surely, 2^138446921 is an apocalyptic number.

It is an amenable number.

138446921 is a deficient number, since it is larger than the sum of its proper divisors (1).

138446921 is an equidigital number, since it uses as much as digits as its factorization.

138446921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 41472, while the sum is 38.

The square root of 138446921 is about 11766.3469692169. The cubic root of 138446921 is about 517.3221818219.

The spelling of 138446921 in words is "one hundred thirty-eight million, four hundred forty-six thousand, nine hundred twenty-one".