138337721 has 4 divisors (see below), whose sum is σ = 146475252. Its totient is φ = 130200192.

The previous prime is 138337711. The next prime is 138337733. The reversal of 138337721 is 127733831.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 89491600 + 48846121 = 9460^2 + 6989^2 .

It is a cyclic number.

It is not a de Polignac number, because 138337721 - 2⁶ = 138337657 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (138337711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4068740 + ... + 4068773.

It is an arithmetic number, because the mean of its divisors is an integer number (36618813).

Almost surely, 2^138337721 is an apocalyptic number.

It is an amenable number.

138337721 is a deficient number, since it is larger than the sum of its proper divisors (8137531).

138337721 is an equidigital number, since it uses as much as digits as its factorization.

138337721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8137530.

The product of its digits is 21168, while the sum is 35.

The square root of 138337721 is about 11761.7057011303. The cubic root of 138337721 is about 517.1861334338.

The spelling of 138337721 in words is "one hundred thirty-eight million, three hundred thirty-seven thousand, seven hundred twenty-one".