217981440 has 120 divisors (see below), whose sum is σ = 755010828. Its totient is φ = 58122240.

The previous prime is 217981427. The next prime is 217981447. The reversal of 217981440 is 44189712.

217981440 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 217149696 + 831744 = 14736^2 + 912^2 .

It is a tau number, because it is divible by the number of its divisors (120).

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 = 217981395 and 217981404.

It is not an unprimeable number, because it can be changed into a prime (217981447) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 18310 + ... + 27770.

Almost surely, 2^217981440 is an apocalyptic number.

217981440 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 217981440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (377505414).

217981440 is an abundant number, since it is smaller than the sum of its proper divisors (537029388).

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

217981440 is an equidigital number, since it uses as much as digits as its factorization.

217981440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9490 (or 9471 counting only the distinct ones).

The product of its (nonzero) digits is 16128, while the sum is 36.

The square root of 217981440 is about 14764.1945259469. The cubic root of 217981440 is about 601.8290850803.

The spelling of 217981440 in words is "two hundred seventeen million, nine hundred eighty-one thousand, four hundred forty".