217312720 has 80 divisors (see below), whose sum is σ = 520680960. Its totient is φ = 84311552.

The previous prime is 217312699. The next prime is 217312723. The reversal of 217312720 is 27213712.

It is a tau number, because it is divible by the number of its divisors (80).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (217312723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 453441 + ... + 453919.

It is an arithmetic number, because the mean of its divisors is an integer number (6508512).

Almost surely, 2^217312720 is an apocalyptic number.

217312720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 217312720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (260340480).

217312720 is an abundant number, since it is smaller than the sum of its proper divisors (303368240).

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

217312720 is a wasteful number, since it uses less digits than its factorization.

217312720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 652 (or 646 counting only the distinct ones).

The product of its (nonzero) digits is 1176, while the sum is 25.

The square root of 217312720 is about 14741.5304497193. The cubic root of 217312720 is about 601.2130274362.

The spelling of 217312720 in words is "two hundred seventeen million, three hundred twelve thousand, seven hundred twenty".