221721984 has 96 divisors (see below), whose sum is σ = 696070440. Its totient is φ = 67184640.

The previous prime is 221721979. The next prime is 221721989. The reversal of 221721984 is 489127122.

It is an interprime number because it is at equal distance from previous prime (221721979) and next prime (221721989).

It is a tau number, because it is divible by the number of its divisors (96).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221721989) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 3924 + ... + 21420.

Almost surely, 2^221721984 is an apocalyptic number.

221721984 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 221721984, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (348035220).

221721984 is an abundant number, since it is smaller than the sum of its proper divisors (474348456).

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

221721984 is a wasteful number, since it uses less digits than its factorization.

221721984 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17528 (or 17513 counting only the distinct ones).

The product of its digits is 16128, while the sum is 36.

The square root of 221721984 is about 14890.3318969055. The cubic root of 221721984 is about 605.2520262279.

The spelling of 221721984 in words is "two hundred twenty-one million, seven hundred twenty-one thousand, nine hundred eighty-four".