138505840 has 40 divisors (see below), whose sum is σ = 351303408. Its totient is φ = 50365440.

The previous prime is 138505823. The next prime is 138505847. The reversal of 138505840 is 48505831.

It is a tau number, because it is divible by the number of its divisors (40).

It is a junction number, because it is equal to n+sod(n) for n = 138505796 and 138505805.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (138505847) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 77817 + ... + 79576.

Almost surely, 2^138505840 is an apocalyptic number.

138505840 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

138505840 is an abundant number, since it is smaller than the sum of its proper divisors (212797568).

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

138505840 is a wasteful number, since it uses less digits than its factorization.

138505840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 157417 (or 157411 counting only the distinct ones).

The product of its (nonzero) digits is 19200, while the sum is 34.

The square root of 138505840 is about 11768.8504111489. The cubic root of 138505840 is about 517.3955571936.

Subtracting from 138505840 its reverse (48505831), we obtain a palindrome (90000009).

The spelling of 138505840 in words is "one hundred thirty-eight million, five hundred five thousand, eight hundred forty".