217312009128 has 192 divisors, whose sum is σ = 616290292800. Its totient is φ = 69106452480.

The previous prime is 217312009067. The next prime is 217312009139. The reversal of 217312009128 is 821900213712.

217312009128 is a `hidden beast` number, since 217 + 312 + 0 + 0 + 9 + 128 = 666.

It is a super-2 number, since 2×217312009128² (a number of 23 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 217312009092 and 217312009101.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 69627408 + ... + 69630528.

It is an arithmetic number, because the mean of its divisors is an integer number (3209845275).

Almost surely, 2^217312009128 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 217312009128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (308145146400).

217312009128 is an abundant number, since it is smaller than the sum of its proper divisors (398978283672).

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

217312009128 is a wasteful number, since it uses less digits than its factorization.

217312009128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3672 (or 3665 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 36.

The spelling of 217312009128 in words is "two hundred seventeen billion, three hundred twelve million, nine thousand, one hundred twenty-eight".