217661664 has 192 divisors, whose sum is σ = 659957760. Its totient is φ = 62208000.

The previous prime is 217661651. The next prime is 217661671. The reversal of 217661664 is 466166712.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1996842 + ... + 1996950.

It is an arithmetic number, because the mean of its divisors is an integer number (3437280).

Almost surely, 2^217661664 is an apocalyptic number.

217661664 is a gapful number since it is divisible by the number (24) 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 217661664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (329978880).

217661664 is an abundant number, since it is smaller than the sum of its proper divisors (442296096).

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

217661664 is a wasteful number, since it uses less digits than its factorization.

217661664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 225 (or 217 counting only the distinct ones).

The product of its digits is 72576, while the sum is 39.

The square root of 217661664 is about 14753.3611085745. The cubic root of 217661664 is about 601.5346491843.

The spelling of 217661664 in words is "two hundred seventeen million, six hundred sixty-one thousand, six hundred sixty-four".