138518621 has 8 divisors (see below), whose sum is σ = 140470200. Its totient is φ = 136576000.

The previous prime is 138518603. The next prime is 138518641. The reversal of 138518621 is 126815831.

It can be written as a sum of positive squares in 4 ways, for example, as 5692996 + 132825625 = 2386^2 + 11525^2 .

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 138518621 - 2⁶ = 138518557 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (138518641) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 32621 + ... + 36621.

It is an arithmetic number, because the mean of its divisors is an integer number (17558775).

Almost surely, 2^138518621 is an apocalyptic number.

It is an amenable number.

138518621 is a deficient number, since it is larger than the sum of its proper divisors (1951579).

138518621 is an equidigital number, since it uses as much as digits as its factorization.

138518621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4479.

The product of its digits is 11520, while the sum is 35.

The square root of 138518621 is about 11769.3933998316. The cubic root of 138518621 is about 517.4114713943.

The spelling of 138518621 in words is "one hundred thirty-eight million, five hundred eighteen thousand, six hundred twenty-one".