138423978 has 144 divisors (see below), whose sum is σ = 391120704. Its totient is φ = 35691840.

The previous prime is 138423973. The next prime is 138423991. The reversal of 138423978 is 879324831.

138423978 is a `hidden beast` number, since 138 + 423 + 97 + 8 = 666.

It is a super-2 number, since 2×138423978² = 38322395370688968, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (138423973) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 1010326 + ... + 1010462.

It is an arithmetic number, because the mean of its divisors is an integer number (2716116).

Almost surely, 2^138423978 is an apocalyptic number.

138423978 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 138423978, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (195560352).

138423978 is an abundant number, since it is smaller than the sum of its proper divisors (252696726).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

138423978 is an equidigital number, since it uses as much as digits as its factorization.

138423978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 181 (or 160 counting only the distinct ones).

The product of its digits is 290304, while the sum is 45.

The square root of 138423978 is about 11765.3719873194. The cubic root of 138423978 is about 517.2936038937.

The spelling of 138423978 in words is "one hundred thirty-eight million, four hundred twenty-three thousand, nine hundred seventy-eight".