138128121 has 12 divisors (see below), whose sum is σ = 201091072. Its totient is φ = 91359576.

The previous prime is 138128117. The next prime is 138128147. The reversal of 138128121 is 121821831.

138128121 is a `hidden beast` number, since 1 + 381 + 281 + 2 + 1 = 666.

It is not a de Polignac number, because 138128121 - 2² = 138128117 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (138128101) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 59281 + ... + 61566.

Almost surely, 2^138128121 is an apocalyptic number.

It is an amenable number.

138128121 is a deficient number, since it is larger than the sum of its proper divisors (62962951).

138128121 is a wasteful number, since it uses less digits than its factorization.

138128121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 120980 (or 120977 counting only the distinct ones).

The product of its digits is 768, while the sum is 27.

The square root of 138128121 is about 11752.7920512532. The cubic root of 138128121 is about 516.9247995358.

Adding to 138128121 its reverse (121821831), we get a palindrome (259949952).

The spelling of 138128121 in words is "one hundred thirty-eight million, one hundred twenty-eight thousand, one hundred twenty-one".