217397840 has 120 divisors (see below), whose sum is σ = 577650528. Its totient is φ = 75454720.

The previous prime is 217397813. The next prime is 217397849. The reversal of 217397840 is 48793712.

217397840 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (217397849) 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, 465287 + ... + 465753.

Almost surely, 2^217397840 is an apocalyptic number.

217397840 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 217397840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (288825264).

217397840 is an abundant number, since it is smaller than the sum of its proper divisors (360252688).

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

217397840 is a wasteful number, since it uses less digits than its factorization.

217397840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 537 (or 508 counting only the distinct ones).

The product of its (nonzero) digits is 84672, while the sum is 41.

The square root of 217397840 is about 14744.4172485724. The cubic root of 217397840 is about 601.2915142864.

The spelling of 217397840 in words is "two hundred seventeen million, three hundred ninety-seven thousand, eight hundred forty".