138017921 has 4 divisors (see below), whose sum is σ = 142470144. Its totient is φ = 133565700.

The previous prime is 138017903. The next prime is 138017939. The reversal of 138017921 is 129710831.

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, and also an emirpimes, since its reverse is a distinct semiprime: 129710831 = 619 ⋅209549.

It is an interprime number because it is at equal distance from previous prime (138017903) and next prime (138017939).

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-138017921 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (138017981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2226065 + ... + 2226126.

It is an arithmetic number, because the mean of its divisors is an integer number (35617536).

Almost surely, 2^138017921 is an apocalyptic number.

It is an amenable number.

138017921 is a deficient number, since it is larger than the sum of its proper divisors (4452223).

138017921 is an equidigital number, since it uses as much as digits as its factorization.

138017921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4452222.

The product of its (nonzero) digits is 3024, while the sum is 32.

The square root of 138017921 is about 11748.1028681230. The cubic root of 138017921 is about 516.7872936986.

The spelling of 138017921 in words is "one hundred thirty-eight million, seventeen thousand, nine hundred twenty-one".