138542640 has 80 divisors (see below), whose sum is σ = 431543808. Its totient is φ = 36767488.

The previous prime is 138542617. The next prime is 138542641. The reversal of 138542640 is 46245831.

It is a tau number, because it is divible by the number of its divisors (80).

It is not an unprimeable number, because it can be changed into a prime (138542641) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 53209 + ... + 55751.

Almost surely, 2^138542640 is an apocalyptic number.

138542640 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 138542640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (215771904).

138542640 is an abundant number, since it is smaller than the sum of its proper divisors (293001168).

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

138542640 is a wasteful number, since it uses less digits than its factorization.

138542640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2786 (or 2780 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 33.

The square root of 138542640 is about 11770.4137565338. The cubic root of 138542640 is about 517.4413758885.

The spelling of 138542640 in words is "one hundred thirty-eight million, five hundred forty-two thousand, six hundred forty".