217709196978 has 128 divisors (see below), whose sum is σ = 555014799360. Its totient is φ = 55404195840.

The previous prime is 217709196961. The next prime is 217709196989. The reversal of 217709196978 is 879691907712.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1762258 + ... + 1881746.

It is an arithmetic number, because the mean of its divisors is an integer number (4336053120).

Almost surely, 2^217709196978 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 217709196978, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (277507399680).

217709196978 is an abundant number, since it is smaller than the sum of its proper divisors (337305602382).

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

217709196978 is a wasteful number, since it uses less digits than its factorization.

217709196978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 119632.

The product of its (nonzero) digits is 24004512, while the sum is 66.

The spelling of 217709196978 in words is "two hundred seventeen billion, seven hundred nine million, one hundred ninety-six thousand, nine hundred seventy-eight".