65721984 has 64 divisors (see below), whose sum is σ = 180238080. Its totient is φ = 21196800.

The previous prime is 65721979. The next prime is 65721989. The reversal of 65721984 is 48912756.

65721984 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (65721979) and next prime (65721989).

It is a tau number, because it is divible by the number of its divisors (64).

It is not an unprimeable number, because it can be changed into a prime (65721989) 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 7 ways as a sum of consecutive naturals, for example, 9144 + ... + 14664.

It is an arithmetic number, because the mean of its divisors is an integer number (2816220).

Almost surely, 2^65721984 is an apocalyptic number.

65721984 is a gapful number since it is divisible by the number (64) 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 65721984, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (90119040).

65721984 is an abundant number, since it is smaller than the sum of its proper divisors (114516096).

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

65721984 is a wasteful number, since it uses less digits than its factorization.

65721984 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5569 (or 5557 counting only the distinct ones).

The product of its digits is 120960, while the sum is 42.

The square root of 65721984 is about 8106.9096454814. The cubic root of 65721984 is about 403.5557643555. Note that the first 3 decimals are identical.

The spelling of 65721984 in words is "sixty-five million, seven hundred twenty-one thousand, nine hundred eighty-four".