128891617221 has 8 divisors (see below), whose sum is σ = 176047087104. Its totient is φ = 83831946080.

The previous prime is 128891617207. The next prime is 128891617243. The reversal of 128891617221 is 122716198821.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 128891617221 - 2⁹ = 128891616709 is a prime.

It is a super-2 number, since 2×128891617221² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128891617321) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 523949541 + ... + 523949786.

It is an arithmetic number, because the mean of its divisors is an integer number (22005885888).

Almost surely, 2^128891617221 is an apocalyptic number.

It is an amenable number.

128891617221 is a deficient number, since it is larger than the sum of its proper divisors (47155469883).

128891617221 is a wasteful number, since it uses less digits than its factorization.

128891617221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1047899371.

The product of its digits is 193536, while the sum is 48.

The spelling of 128891617221 in words is "one hundred twenty-eight billion, eight hundred ninety-one million, six hundred seventeen thousand, two hundred twenty-one".