138840561 has 20 divisors (see below), whose sum is σ = 207885744. Its totient is φ = 92345400.

The previous prime is 138840553. The next prime is 138840563. The reversal of 138840561 is 165048831.

138840561 is a `hidden beast` number, since 13 + 8 + 84 + 0 + 561 = 666.

It is not a de Polignac number, because 138840561 - 2³ = 138840553 is a prime.

It is not an unprimeable number, because it can be changed into a prime (138840563) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 38026 + ... + 41516.

Almost surely, 2^138840561 is an apocalyptic number.

It is an amenable number.

138840561 is a deficient number, since it is larger than the sum of its proper divisors (69045183).

138840561 is an equidigital number, since it uses as much as digits as its factorization.

138840561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3994 (or 3985 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 36.

The square root of 138840561 is about 11783.0624627047. The cubic root of 138840561 is about 517.8120109625.

The spelling of 138840561 in words is "one hundred thirty-eight million, eight hundred forty thousand, five hundred sixty-one".