138640657 has 2 divisors, whose sum is σ = 138640658. Its totient is φ = 138640656.

The previous prime is 138640637. The next prime is 138640669. The reversal of 138640657 is 756046831.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 97693456 + 40947201 = 9884^2 + 6399^2 .

It is a cyclic number.

It is not a de Polignac number, because 138640657 - 2¹⁹ = 138116369 is a prime.

It is a Chen prime.

It is equal to p_7839580 and since 138640657 and 7839580 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (138640637) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69320328 + 69320329.

It is an arithmetic number, because the mean of its divisors is an integer number (69320329).

Almost surely, 2^138640657 is an apocalyptic number.

It is an amenable number.

138640657 is a deficient number, since it is larger than the sum of its proper divisors (1).

138640657 is an equidigital number, since it uses as much as digits as its factorization.

138640657 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 120960, while the sum is 40.

The square root of 138640657 is about 11774.5767227531. The cubic root of 138640657 is about 517.5633746591.

The spelling of 138640657 in words is "one hundred thirty-eight million, six hundred forty thousand, six hundred fifty-seven".