138643261 has 2 divisors, whose sum is σ = 138643262. Its totient is φ = 138643260.

The previous prime is 138643243. The next prime is 138643321. The reversal of 138643261 is 162346831.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 110880900 + 27762361 = 10530^2 + 5269^2 .

It is an emirp because it is prime and its reverse (162346831) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-138643261 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (138643231) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69321630 + 69321631.

It is an arithmetic number, because the mean of its divisors is an integer number (69321631).

Almost surely, 2^138643261 is an apocalyptic number.

It is an amenable number.

138643261 is a deficient number, since it is larger than the sum of its proper divisors (1).

138643261 is an equidigital number, since it uses as much as digits as its factorization.

138643261 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 20736, while the sum is 34.

The square root of 138643261 is about 11774.6872994573. The cubic root of 138643261 is about 517.5666149942.

The spelling of 138643261 in words is "one hundred thirty-eight million, six hundred forty-three thousand, two hundred sixty-one".