15991421717 has 4 divisors (see below), whose sum is σ = 16023991296. Its totient is φ = 15958852140.

The previous prime is 15991421647. The next prime is 15991421731. The reversal of 15991421717 is 71712419951.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 71712419951 = 17159 ⋅4179289.

It is a cyclic number.

It is not a de Polignac number, because 15991421717 - 2⁸ = 15991421461 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 (15991421417) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16284053 + ... + 16285034.

It is an arithmetic number, because the mean of its divisors is an integer number (4005997824).

Almost surely, 2^15991421717 is an apocalyptic number.

It is an amenable number.

15991421717 is a deficient number, since it is larger than the sum of its proper divisors (32569579).

15991421717 is an equidigital number, since it uses as much as digits as its factorization.

15991421717 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32569578.

The product of its digits is 158760, while the sum is 47.

The spelling of 15991421717 in words is "fifteen billion, nine hundred ninety-one million, four hundred twenty-one thousand, seven hundred seventeen".