138891681 has 12 divisors (see below), whose sum is σ = 202690852. Its totient is φ = 91639296.

The previous prime is 138891659. The next prime is 138891703. The reversal of 138891681 is 186198831.

It is an interprime number because it is at equal distance from previous prime (138891659) and next prime (138891703).

It can be written as a sum of positive squares in 2 ways, for example, as 24059025 + 114832656 = 4905^2 + 10716^2 .

It is not a de Polignac number, because 138891681 - 2¹⁹ = 138367393 is a prime.

It is a super-2 number, since 2×138891681² = 38581798102011522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (138891481) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 78676 + ... + 80421.

Almost surely, 2^138891681 is an apocalyptic number.

It is an amenable number.

138891681 is a deficient number, since it is larger than the sum of its proper divisors (63799171).

138891681 is a wasteful number, since it uses less digits than its factorization.

138891681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 159200 (or 159197 counting only the distinct ones).

The product of its digits is 82944, while the sum is 45.

The square root of 138891681 is about 11785.2314784225. The cubic root of 138891681 is about 517.8755545978.

The spelling of 138891681 in words is "one hundred thirty-eight million, eight hundred ninety-one thousand, six hundred eighty-one".