138993408 has 90 divisors (see below), whose sum is σ = 414515024. Its totient is φ = 46324224.

The previous prime is 138993383. The next prime is 138993409. The reversal of 138993408 is 804399831.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (138993409) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 17385 + ... + 24087.

Almost surely, 2^138993408 is an apocalyptic number.

138993408 is a gapful number since it is divisible by the number (18) 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 138993408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (207257512).

138993408 is an abundant number, since it is smaller than the sum of its proper divisors (275521616).

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

138993408 is an frugal number, since it uses more digits than its factorization.

138993408 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6731 (or 6708 counting only the distinct ones).

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

The square root of 138993408 is about 11789.5465561658. The cubic root of 138993408 is about 518.0019578247.

The spelling of 138993408 in words is "one hundred thirty-eight million, nine hundred ninety-three thousand, four hundred eight".