138624221 has 4 divisors (see below), whose sum is σ = 138792672. Its totient is φ = 138455772.

The previous prime is 138624149. The next prime is 138624229. The reversal of 138624221 is 122426831.

It is a happy number.

138624221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 138624221 - 2¹⁴ = 138607837 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 (138624229) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 82985 + ... + 84638.

It is an arithmetic number, because the mean of its divisors is an integer number (34698168).

Almost surely, 2^138624221 is an apocalyptic number.

It is an amenable number.

138624221 is a deficient number, since it is larger than the sum of its proper divisors (168451).

138624221 is an equidigital number, since it uses as much as digits as its factorization.

138624221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 168450.

The product of its digits is 4608, while the sum is 29.

The square root of 138624221 is about 11773.8787576567. The cubic root of 138624221 is about 517.5429212846.

The spelling of 138624221 in words is "one hundred thirty-eight million, six hundred twenty-four thousand, two hundred twenty-one".