138040781 has 2 divisors, whose sum is σ = 138040782. Its totient is φ = 138040780.

The previous prime is 138040717. The next prime is 138040787. The reversal of 138040781 is 187040831.

138040781 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 137686756 + 354025 = 11734^2 + 595^2 .

It is a cyclic number.

It is not a de Polignac number, because 138040781 - 2⁶ = 138040717 is a prime.

It is a super-2 number, since 2×138040781² = 38110514438179922, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (138040787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69020390 + 69020391.

It is an arithmetic number, because the mean of its divisors is an integer number (69020391).

Almost surely, 2^138040781 is an apocalyptic number.

It is an amenable number.

138040781 is a deficient number, since it is larger than the sum of its proper divisors (1).

138040781 is an equidigital number, since it uses as much as digits as its factorization.

138040781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5376, while the sum is 32.

The square root of 138040781 is about 11749.0757508836. The cubic root of 138040781 is about 516.8158240645.

Subtracting 138040781 from its reverse (187040831), we obtain a triangular number (49000050 = T₉₈₉₉).

The spelling of 138040781 in words is "one hundred thirty-eight million, forty thousand, seven hundred eighty-one".