217121664 has 64 divisors (see below), whose sum is σ = 607104000. Its totient is φ = 68562432.

The previous prime is 217121659. The next prime is 217121669. The reversal of 217121664 is 466121712.

217121664 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (217121659) and next prime (217121669).

It is a tau number, because it is divible by the number of its divisors (64).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (217121669) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7584 + ... + 22175.

It is an arithmetic number, because the mean of its divisors is an integer number (9486000).

Almost surely, 2^217121664 is an apocalyptic number.

217121664 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

217121664 is an abundant number, since it is smaller than the sum of its proper divisors (389982336).

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

217121664 is a wasteful number, since it uses less digits than its factorization.

217121664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29795 (or 29783 counting only the distinct ones).

The product of its digits is 4032, while the sum is 30.

The square root of 217121664 is about 14735.0488292370. The cubic root of 217121664 is about 601.0367852066.

The spelling of 217121664 in words is "two hundred seventeen million, one hundred twenty-one thousand, six hundred sixty-four".