138209261 has 2 divisors, whose sum is σ = 138209262. Its totient is φ = 138209260.

The previous prime is 138209233. The next prime is 138209293. The reversal of 138209261 is 162902831.

It is an a-pointer prime, because the next prime (138209293) can be obtained adding 138209261 to its sum of digits (32).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 137616361 + 592900 = 11731^2 + 770^2 .

It is a cyclic number.

It is not a de Polignac number, because 138209261 - 2²² = 134014957 is a prime.

It is a super-2 number, since 2×138209261² = 38203599652332242, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (138209161) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69104630 + 69104631.

It is an arithmetic number, because the mean of its divisors is an integer number (69104631).

Almost surely, 2^138209261 is an apocalyptic number.

It is an amenable number.

138209261 is a deficient number, since it is larger than the sum of its proper divisors (1).

138209261 is an equidigital number, since it uses as much as digits as its factorization.

138209261 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5184, while the sum is 32.

The square root of 138209261 is about 11756.2434901630. The cubic root of 138209261 is about 517.0259980167.

The spelling of 138209261 in words is "one hundred thirty-eight million, two hundred nine thousand, two hundred sixty-one".