16091721 has 12 divisors (see below), whose sum is σ = 23811060. Its totient is φ = 10465920.

The previous prime is 16091717. The next prime is 16091731. The reversal of 16091721 is 12719061.

16091721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 881721 + 15210000 = 939^2 + 3900^2 .

It is not a de Polignac number, because 16091721 - 2² = 16091717 is a prime.

It is not an unprimeable number, because it can be changed into a prime (16091731) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 21436 + ... + 22173.

It is an arithmetic number, because the mean of its divisors is an integer number (1984255).

Almost surely, 2^16091721 is an apocalyptic number.

It is an amenable number.

16091721 is a deficient number, since it is larger than the sum of its proper divisors (7719339).

16091721 is a wasteful number, since it uses less digits than its factorization.

16091721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43656 (or 43653 counting only the distinct ones).

The product of its (nonzero) digits is 756, while the sum is 27.

The square root of 16091721 is about 4011.4487407918. The cubic root of 16091721 is about 252.4647978897.

The spelling of 16091721 in words is "sixteen million, ninety-one thousand, seven hundred twenty-one".