217989978 has 16 divisors (see below), whose sum is σ = 436124736. Its totient is φ = 72639200.

The previous prime is 217989971. The next prime is 217989991. The reversal of 217989978 is 879989712.

It is not an unprimeable number, because it can be changed into a prime (217989971) 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, 31675 + ... + 37937.

It is an arithmetic number, because the mean of its divisors is an integer number (27257796).

Almost surely, 2^217989978 is an apocalyptic number.

217989978 is an abundant number, since it is smaller than the sum of its proper divisors (218134758).

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

217989978 is a wasteful number, since it uses less digits than its factorization.

217989978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12069.

The product of its digits is 4572288, while the sum is 60.

The square root of 217989978 is about 14764.4836685879. The cubic root of 217989978 is about 601.8369425530.

The spelling of 217989978 in words is "two hundred seventeen million, nine hundred eighty-nine thousand, nine hundred seventy-eight".