138521645 has 8 divisors (see below), whose sum is σ = 166301304. Its totient is φ = 110767104.

The previous prime is 138521641. The next prime is 138521651. The reversal of 138521645 is 546125831.

It can be written as a sum of positive squares in 4 ways, for example, as 5373124 + 133148521 = 2318^2 + 11539^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 138521645 - 2² = 138521641 is a prime.

It is a super-3 number, since 3×138521645³ (a number of 25 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (138521641) 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, 9437 + ... + 19133.

It is an arithmetic number, because the mean of its divisors is an integer number (20787663).

Almost surely, 2^138521645 is an apocalyptic number.

It is an amenable number.

138521645 is a deficient number, since it is larger than the sum of its proper divisors (27779659).

138521645 is an equidigital number, since it uses as much as digits as its factorization.

138521645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12559.

The product of its digits is 28800, while the sum is 35.

The square root of 138521645 is about 11769.5218679435. The cubic root of 138521645 is about 517.4152365702.

The spelling of 138521645 in words is "one hundred thirty-eight million, five hundred twenty-one thousand, six hundred forty-five".