138644815 has 4 divisors (see below), whose sum is σ = 166373784. Its totient is φ = 110915848.

The previous prime is 138644797. The next prime is 138644819. The reversal of 138644815 is 518446831.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 518446831 = 7 ⋅74063833.

It is a cyclic number.

It is not a de Polignac number, because 138644815 - 2²⁵ = 105090383 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 (138644819) 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, 13864477 + ... + 13864486.

It is an arithmetic number, because the mean of its divisors is an integer number (41593446).

Almost surely, 2^138644815 is an apocalyptic number.

138644815 is a deficient number, since it is larger than the sum of its proper divisors (27728969).

138644815 is an equidigital number, since it uses as much as digits as its factorization.

138644815 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27728968.

The product of its digits is 92160, while the sum is 40.

The square root of 138644815 is about 11774.7532882859. The cubic root of 138644815 is about 517.5685487233.

It can be divided in two parts, 138 and 644815, that multiplied together give a triangular number (88984470 = T₁₃₃₄₀).

The spelling of 138644815 in words is "one hundred thirty-eight million, six hundred forty-four thousand, eight hundred fifteen".