138939840 has 224 divisors, whose sum is σ = 528279360. Its totient is φ = 34172928.

The previous prime is 138939839. The next prime is 138939851. The reversal of 138939840 is 48939831.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 111702 + ... + 112938.

It is an arithmetic number, because the mean of its divisors is an integer number (2358390).

Almost surely, 2^138939840 is an apocalyptic number.

138939840 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 138939840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (264139680).

138939840 is an abundant number, since it is smaller than the sum of its proper divisors (389339520).

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

138939840 is a wasteful number, since it uses less digits than its factorization.

138939840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1276 (or 1260 counting only the distinct ones).

The product of its (nonzero) digits is 186624, while the sum is 45.

The square root of 138939840 is about 11787.2744941314. The cubic root of 138939840 is about 517.9354033629.

Subtracting from 138939840 its reverse (48939831), we obtain a palindrome (90000009).

The spelling of 138939840 in words is "one hundred thirty-eight million, nine hundred thirty-nine thousand, eight hundred forty".