138778 has 4 divisors (see below), whose sum is σ = 208170. Its totient is φ = 69388.

The previous prime is 138763. The next prime is 138793. The reversal of 138778 is 877831.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 877831 = 131 ⋅6701.

It is an interprime number because it is at equal distance from previous prime (138763) and next prime (138793).

It can be written as a sum of positive squares in only one way, i.e., 110889 + 27889 = 333^2 + 167^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 34693 + ... + 34696.

2¹³⁸⁷⁷⁸ is an apocalyptic number.

138778 is a deficient number, since it is larger than the sum of its proper divisors (69392).

138778 is an equidigital number, since it uses as much as digits as its factorization.

138778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 69391.

The product of its digits is 9408, while the sum is 34.

The square root of 138778 is about 372.5291934869. The cubic root of 138778 is about 51.7734224606.

The spelling of 138778 in words is "one hundred thirty-eight thousand, seven hundred seventy-eight".