138735921 has 4 divisors (see below), whose sum is σ = 184981232. Its totient is φ = 92490612.

The previous prime is 138735901. The next prime is 138735937. The reversal of 138735921 is 129537831.

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 not a de Polignac number, because 138735921 - 2²¹ = 136638769 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 138735921.

It is not an unprimeable number, because it can be changed into a prime (138735901) 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 3 ways as a sum of consecutive naturals, for example, 23122651 + ... + 23122656.

It is an arithmetic number, because the mean of its divisors is an integer number (46245308).

Almost surely, 2^138735921 is an apocalyptic number.

It is an amenable number.

138735921 is a deficient number, since it is larger than the sum of its proper divisors (46245311).

138735921 is an equidigital number, since it uses as much as digits as its factorization.

138735921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 46245310.

The product of its digits is 45360, while the sum is 39.

The square root of 138735921 is about 11778.6213539616. The cubic root of 138735921 is about 517.6818917658.

It can be divided in two parts, 138735 and 921, that added together give a triangular number (139656 = T₅₂₈).

The spelling of 138735921 in words is "one hundred thirty-eight million, seven hundred thirty-five thousand, nine hundred twenty-one".