221681664 has 192 divisors, whose sum is σ = 694512000. Its totient is φ = 69672960.

The previous prime is 221681653. The next prime is 221681699. The reversal of 221681664 is 466186122.

It is a tau number, because it is divible by the number of its divisors (192).

It is a super-3 number, since 3×221681664³ (a number of 26 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a nude number because it is divisible by every one of its digits and also a Zuckerman number because it is divisible by the product of its digits.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1050519 + ... + 1050729.

It is an arithmetic number, because the mean of its divisors is an integer number (3617250).

Almost surely, 2^221681664 is an apocalyptic number.

221681664 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 221681664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (347256000).

221681664 is an abundant number, since it is smaller than the sum of its proper divisors (472830336).

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

221681664 is a wasteful number, since it uses less digits than its factorization.

221681664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 261 (or 235 counting only the distinct ones).

The product of its digits is 27648, while the sum is 36.

The square root of 221681664 is about 14888.9779367155. The cubic root of 221681664 is about 605.2153357734.

It can be divided in two parts, 22168 and 1664, that added together give a palindrome (23832).

The spelling of 221681664 in words is "two hundred twenty-one million, six hundred eighty-one thousand, six hundred sixty-four".