217664640 has 384 divisors, whose sum is σ = 824878080. Its totient is φ = 52715520.

The previous prime is 217664569. The next prime is 217664659. The reversal of 217664640 is 46466712.

217664640 is a `hidden beast` number, since 2 + 1 + 7 + 6 + 6 + 4 + 640 = 666.

It is a tau number, because it is divible by the number of its divisors (384).

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 = 217664595 and 217664604.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 4106854 + ... + 4106906.

It is an arithmetic number, because the mean of its divisors is an integer number (2148120).

Almost surely, 2^217664640 is an apocalyptic number.

217664640 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 217664640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (412439040).

217664640 is an abundant number, since it is smaller than the sum of its proper divisors (607213440).

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

217664640 is a wasteful number, since it uses less digits than its factorization.

217664640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 132 (or 117 counting only the distinct ones).

The product of its (nonzero) digits is 48384, while the sum is 36.

The square root of 217664640 is about 14753.4619666030. The cubic root of 217664640 is about 601.5373906852.

The spelling of 217664640 in words is "two hundred seventeen million, six hundred sixty-four thousand, six hundred forty".