221720688 has 180 divisors, whose sum is σ = 734588400. Its totient is φ = 62403264.

The previous prime is 221720669. The next prime is 221720693. The reversal of 221720688 is 886027122.

It is a happy number.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 3309231 + ... + 3309297.

Almost surely, 2^221720688 is an apocalyptic number.

221720688 is a gapful number since it is divisible by the number (28) 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 221720688, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (367294200).

221720688 is an abundant number, since it is smaller than the sum of its proper divisors (512867712).

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

221720688 is an equidigital number, since it uses as much as digits as its factorization.

221720688 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 169 (or 79 counting only the distinct ones).

The product of its (nonzero) digits is 21504, while the sum is 36.

The square root of 221720688 is about 14890.2883786715. The cubic root of 221720688 is about 605.2508469611.

The spelling of 221720688 in words is "two hundred twenty-one million, seven hundred twenty thousand, six hundred eighty-eight".