138923987 has 4 divisors (see below), whose sum is σ = 139322400. Its totient is φ = 138525576.

The previous prime is 138923977. The next prime is 138923999. The reversal of 138923987 is 789329831.

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: 789329831 = 5813 ⋅135787.

It is a cyclic number.

It is not a de Polignac number, because 138923987 - 2⁶ = 138923923 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (138923957) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 198683 + ... + 199380.

It is an arithmetic number, because the mean of its divisors is an integer number (34830600).

Almost surely, 2^138923987 is an apocalyptic number.

138923987 is a deficient number, since it is larger than the sum of its proper divisors (398413).

138923987 is an equidigital number, since it uses as much as digits as its factorization.

138923987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 398412.

The product of its digits is 653184, while the sum is 50.

The square root of 138923987 is about 11786.6020124546. The cubic root of 138923987 is about 517.9157038482.

The spelling of 138923987 in words is "one hundred thirty-eight million, nine hundred twenty-three thousand, nine hundred eighty-seven".