128921957 has 4 divisors (see below), whose sum is σ = 129381036. Its totient is φ = 128462880.

The previous prime is 128921953. The next prime is 128921977. The reversal of 128921957 is 759129821.

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: 759129821 = 2801 ⋅271021.

It can be written as a sum of positive squares in 2 ways, for example, as 103510276 + 25411681 = 10174^2 + 5041^2 .

It is a cyclic number.

It is not a de Polignac number, because 128921957 - 2² = 128921953 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 (128921953) 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, 229118 + ... + 229679.

It is an arithmetic number, because the mean of its divisors is an integer number (32345259).

Almost surely, 2^128921957 is an apocalyptic number.

It is an amenable number.

128921957 is a deficient number, since it is larger than the sum of its proper divisors (459079).

128921957 is an equidigital number, since it uses as much as digits as its factorization.

128921957 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 459078.

The product of its digits is 90720, while the sum is 44.

The square root of 128921957 is about 11354.3805203102. The cubic root of 128921957 is about 505.1755191609.

The spelling of 128921957 in words is "one hundred twenty-eight million, nine hundred twenty-one thousand, nine hundred fifty-seven".