221009664 has 72 divisors (see below), whose sum is σ = 607247872. Its totient is φ = 71285760.

The previous prime is 221009647. The next prime is 221009669. The reversal of 221009664 is 466900122.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221009669) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19167 + ... + 28449.

Almost surely, 2^221009664 is an apocalyptic number.

221009664 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 221009664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (303623936).

221009664 is an abundant number, since it is smaller than the sum of its proper divisors (386238208).

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

221009664 is an equidigital number, since it uses as much as digits as its factorization.

221009664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9333 (or 9319 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 30.

The square root of 221009664 is about 14866.3937792593. The cubic root of 221009664 is about 604.6031721423.

Adding to 221009664 its reverse (466900122), we get a palindrome (687909786).

The spelling of 221009664 in words is "two hundred twenty-one million, nine thousand, six hundred sixty-four".