216661664 has 48 divisors (see below), whose sum is σ = 436195368. Its totient is φ = 105910272.

The previous prime is 216661661. The next prime is 216661667. The reversal of 216661664 is 466166612.

It is an interprime number because it is at equal distance from previous prime (216661661) and next prime (216661667).

It can be written as a sum of positive squares in 4 ways, for example, as 216325264 + 336400 = 14708^2 + 580^2 .

It is not an unprimeable number, because it can be changed into a prime (216661661) 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, 319694 + ... + 320370.

Almost surely, 2^216661664 is an apocalyptic number.

It is an amenable number.

216661664 is an abundant number, since it is smaller than the sum of its proper divisors (219533704).

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

216661664 is a wasteful number, since it uses less digits than its factorization.

216661664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 897 (or 889 counting only the distinct ones).

The product of its digits is 62208, while the sum is 38.

The square root of 216661664 is about 14719.4315107615. The cubic root of 216661664 is about 600.6120273438.

The spelling of 216661664 in words is "two hundred sixteen million, six hundred sixty-one thousand, six hundred sixty-four".