16543721 has 4 divisors (see below), whose sum is σ = 16562244. Its totient is φ = 16525200.

The previous prime is 16543697. The next prime is 16543733. The reversal of 16543721 is 12734561.

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 7155625 + 9388096 = 2675^2 + 3064^2 .

It is a cyclic number.

It is not a de Polignac number, because 16543721 - 2²² = 12349417 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16543741) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7850 + ... + 9731.

It is an arithmetic number, because the mean of its divisors is an integer number (4140561).

Almost surely, 2^16543721 is an apocalyptic number.

It is an amenable number.

16543721 is a deficient number, since it is larger than the sum of its proper divisors (18523).

16543721 is an equidigital number, since it uses as much as digits as its factorization.

16543721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18522.

The product of its digits is 5040, while the sum is 29.

The square root of 16543721 is about 4067.3973250716. The cubic root of 16543721 is about 254.8068305096.

The spelling of 16543721 in words is "sixteen million, five hundred forty-three thousand, seven hundred twenty-one".