217609728 has 160 divisors (see below), whose sum is σ = 681694464. Its totient is φ = 60383232.

The previous prime is 217609723. The next prime is 217609729. The reversal of 217609728 is 827906712.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a self number, because there is not a number n which added to its sum of digits gives 217609728.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (217609723) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 397551 + ... + 398097.

Almost surely, 2^217609728 is an apocalyptic number.

217609728 is a gapful number since it is divisible by the number (28) 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 217609728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (340847232).

217609728 is an abundant number, since it is smaller than the sum of its proper divisors (464084736).

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

217609728 is an equidigital number, since it uses as much as digits as its factorization.

217609728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 612 (or 596 counting only the distinct ones).

The product of its (nonzero) digits is 84672, while the sum is 42.

The square root of 217609728 is about 14751.6008622793. The cubic root of 217609728 is about 601.4868015476.

The spelling of 217609728 in words is "two hundred seventeen million, six hundred nine thousand, seven hundred twenty-eight".