138681 has 12 divisors (see below), whose sum is σ = 211120. Its totient is φ = 87480.

The previous prime is 138679. The next prime is 138683. The reversal of 138681 is 186831.

It is an interprime number because it is at equal distance from previous prime (138679) and next prime (138683).

It is not a de Polignac number, because 138681 - 2¹ = 138679 is a prime.

It is a super-2 number, since 2×138681² = 38464839522, which contains 22 as substring.

It is an Ulam number.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (138683) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 235 + ... + 576.

2¹³⁸⁶⁸¹ is an apocalyptic number.

It is an amenable number.

138681 is a deficient number, since it is larger than the sum of its proper divisors (72439).

138681 is a wasteful number, since it uses less digits than its factorization.

138681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 836 (or 833 counting only the distinct ones).

The product of its digits is 1152, while the sum is 27.

The square root of 138681 is about 372.3989795904. The cubic root of 138681 is about 51.7613571657.

The spelling of 138681 in words is "one hundred thirty-eight thousand, six hundred eighty-one".