16005345721 has 4 divisors (see below), whose sum is σ = 16012837492. Its totient is φ = 15997853952.

The previous prime is 16005345701. The next prime is 16005345779. The reversal of 16005345721 is 12754350061.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7567086121 + 8438259600 = 86989^2 + 91860^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-16005345721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16005345701) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3742680 + ... + 3746953.

It is an arithmetic number, because the mean of its divisors is an integer number (4003209373).

Almost surely, 2^16005345721 is an apocalyptic number.

It is an amenable number.

16005345721 is a deficient number, since it is larger than the sum of its proper divisors (7491771).

16005345721 is an equidigital number, since it uses as much as digits as its factorization.

16005345721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7491770.

The product of its (nonzero) digits is 25200, while the sum is 34.

Adding to 16005345721 its reverse (12754350061), we get a palindrome (28759695782).

The spelling of 16005345721 in words is "sixteen billion, five million, three hundred forty-five thousand, seven hundred twenty-one".