128121647 has 4 divisors (see below), whose sum is σ = 129743520. Its totient is φ = 126499776.

The previous prime is 128121629. The next prime is 128121649. The reversal of 128121647 is 746121821.

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: 746121821 = 149 ⋅5007529.

It is a cyclic number.

It is not a de Polignac number, because 128121647 - 2⁶ = 128121583 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128121649) 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, 810818 + ... + 810975.

It is an arithmetic number, because the mean of its divisors is an integer number (32435880).

Almost surely, 2^128121647 is an apocalyptic number.

128121647 is a deficient number, since it is larger than the sum of its proper divisors (1621873).

128121647 is an equidigital number, since it uses as much as digits as its factorization.

128121647 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1621872.

The product of its digits is 5376, while the sum is 32.

The square root of 128121647 is about 11319.0833109400. The cubic root of 128121647 is about 504.1280210920.

The spelling of 128121647 in words is "one hundred twenty-eight million, one hundred twenty-one thousand, six hundred forty-seven".