138571781 has 2 divisors, whose sum is σ = 138571782. Its totient is φ = 138571780.

The previous prime is 138571751. The next prime is 138571813. The reversal of 138571781 is 187175831.

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., 103347556 + 35224225 = 10166^2 + 5935^2 .

It is a cyclic number.

It is not a de Polignac number, because 138571781 - 2⁶ = 138571717 is a prime.

It is a super-2 number, since 2×138571781² = 38404276979023922, 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 (138571721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69285890 + 69285891.

It is an arithmetic number, because the mean of its divisors is an integer number (69285891).

Almost surely, 2^138571781 is an apocalyptic number.

It is an amenable number.

138571781 is a deficient number, since it is larger than the sum of its proper divisors (1).

138571781 is an equidigital number, since it uses as much as digits as its factorization.

138571781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 47040, while the sum is 41.

The square root of 138571781 is about 11771.6515833591. The cubic root of 138571781 is about 517.4776528114.

The spelling of 138571781 in words is "one hundred thirty-eight million, five hundred seventy-one thousand, seven hundred eighty-one".