138666 has 24 divisors (see below), whose sum is σ = 306432. Its totient is φ = 41800.

The previous prime is 138661. The next prime is 138679. The reversal of 138666 is 666831.

138666 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

138666 is a modest number, since divided by 666 gives 138 as remainder.

It is a nialpdrome in base 11.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 138666.

It is not an unprimeable number, because it can be changed into a prime (138661) by changing a digit.

138666 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 631 + ... + 821.

It is an arithmetic number, because the mean of its divisors is an integer number (12768).

2¹³⁸⁶⁶⁶ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 138666, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (153216).

138666 is an abundant number, since it is smaller than the sum of its proper divisors (167766).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

138666 is a wasteful number, since it uses less digits than its factorization.

138666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 218 (or 207 counting only the distinct ones).

The product of its digits is 5184, while the sum is 30.

The square root of 138666 is about 372.3788393558. The cubic root of 138666 is about 51.7594908962.

The spelling of 138666 in words is "one hundred thirty-eight thousand, six hundred sixty-six".