138431978 has 8 divisors (see below), whose sum is σ = 208891872. Its totient is φ = 68801356.

The previous prime is 138431959. The next prime is 138431981. The reversal of 138431978 is 879134831.

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

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, 206900 + ... + 207567.

It is an arithmetic number, because the mean of its divisors is an integer number (26111484).

Almost surely, 2^138431978 is an apocalyptic number.

138431978 is a deficient number, since it is larger than the sum of its proper divisors (70459894).

138431978 is a wasteful number, since it uses less digits than its factorization.

138431978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 414636.

The product of its digits is 145152, while the sum is 44.

The square root of 138431978 is about 11765.7119631580. The cubic root of 138431978 is about 517.3035690967.

The spelling of 138431978 in words is "one hundred thirty-eight million, four hundred thirty-one thousand, nine hundred seventy-eight".