138643281 has 24 divisors (see below), whose sum is σ = 230053824. Its totient is φ = 78815520.

The previous prime is 138643261. The next prime is 138643321. The reversal of 138643281 is 182346831.

138643281 is a `hidden beast` number, since 1 + 3 + 8 + 643 + 2 + 8 + 1 = 666.

It is not a de Polignac number, because 138643281 - 2¹⁴ = 138626897 is a prime.

It is a super-2 number, since 2×138643281² = 38443918732889922, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (138643231) 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 23 ways as a sum of consecutive naturals, for example, 6826 + ... + 17996.

It is an arithmetic number, because the mean of its divisors is an integer number (9585576).

Almost surely, 2^138643281 is an apocalyptic number.

It is an amenable number.

138643281 is a deficient number, since it is larger than the sum of its proper divisors (91410543).

138643281 is a wasteful number, since it uses less digits than its factorization.

138643281 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11381 (or 11378 counting only the distinct ones).

The product of its digits is 27648, while the sum is 36.

The square root of 138643281 is about 11774.6881487367. The cubic root of 138643281 is about 517.5666398814.

The spelling of 138643281 in words is "one hundred thirty-eight million, six hundred forty-three thousand, two hundred eighty-one".