16721506261 has 4 divisors (see below), whose sum is σ = 16721980812. Its totient is φ = 16721031712.

The previous prime is 16721506231. The next prime is 16721506303. The reversal of 16721506261 is 16260512761.

It is a happy number.

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 14563903761 + 2157602500 = 120681^2 + 46450^2 .

It is a cyclic number.

It is not a de Polignac number, because 16721506261 - 2¹⁹ = 16720981973 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 16721506261.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16721506231) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 179776 + ... + 256441.

It is an arithmetic number, because the mean of its divisors is an integer number (4180495203).

Almost surely, 2^16721506261 is an apocalyptic number.

It is an amenable number.

16721506261 is a deficient number, since it is larger than the sum of its proper divisors (474551).

16721506261 is an equidigital number, since it uses as much as digits as its factorization.

16721506261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 474550.

The product of its (nonzero) digits is 30240, while the sum is 37.

The spelling of 16721506261 in words is "sixteen billion, seven hundred twenty-one million, five hundred six thousand, two hundred sixty-one".