138221568 has 72 divisors (see below), whose sum is σ = 399262500. Its totient is φ = 46067712.

The previous prime is 138221563. The next prime is 138221621. The reversal of 138221568 is 865122831.

It is a happy number.

138221568 is a `hidden beast` number, since 1 + 382 + 215 + 68 = 666.

It is a tau number, because it is divible by the number of its divisors (72).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (138221563) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 14683 + ... + 22181.

Almost surely, 2^138221568 is an apocalyptic number.

138221568 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 138221568, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (199631250).

138221568 is an abundant number, since it is smaller than the sum of its proper divisors (261040932).

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

138221568 is an equidigital number, since it uses as much as digits as its factorization.

138221568 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7527 (or 7504 counting only the distinct ones).

The product of its digits is 23040, while the sum is 36.

The square root of 138221568 is about 11756.7669025119. The cubic root of 138221568 is about 517.0413439495.

The spelling of 138221568 in words is "one hundred thirty-eight million, two hundred twenty-one thousand, five hundred sixty-eight".