16643779717 has 4 divisors (see below), whose sum is σ = 16668960076. Its totient is φ = 16618599360.

The previous prime is 16643779697. The next prime is 16643779721. The reversal of 16643779717 is 71797734661.

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 6962400481 + 9681379236 = 83441^2 + 98394^2 .

It is a cyclic number.

It is not a de Polignac number, because 16643779717 - 2¹⁹ = 16643255429 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16643719717) 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, 12589188 + ... + 12590509.

It is an arithmetic number, because the mean of its divisors is an integer number (4167240019).

Almost surely, 2^16643779717 is an apocalyptic number.

It is an amenable number.

16643779717 is a deficient number, since it is larger than the sum of its proper divisors (25180359).

16643779717 is an equidigital number, since it uses as much as digits as its factorization.

16643779717 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25180358.

The product of its digits is 9335088, while the sum is 58.

The spelling of 16643779717 in words is "sixteen billion, six hundred forty-three million, seven hundred seventy-nine thousand, seven hundred seventeen".