217608721812 has 72 divisors (see below), whose sum is σ = 569578595040. Its totient is φ = 69968001600.

The previous prime is 217608721801. The next prime is 217608721817. The reversal of 217608721812 is 218127806712.

217608721812 is a `hidden beast` number, since 2 + 1 + 7 + 608 + 7 + 21 + 8 + 12 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (217608721817) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 998083 + ... + 1196405.

It is an arithmetic number, because the mean of its divisors is an integer number (7910813820).

Almost surely, 2^217608721812 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 217608721812, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (284789297520).

217608721812 is an abundant number, since it is smaller than the sum of its proper divisors (351969873228).

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

217608721812 is a wasteful number, since it uses less digits than its factorization.

217608721812 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 199413 (or 199408 counting only the distinct ones).

The product of its (nonzero) digits is 150528, while the sum is 45.

The spelling of 217608721812 in words is "two hundred seventeen billion, six hundred eight million, seven hundred twenty-one thousand, eight hundred twelve".