20716217491 has 2 divisors, whose sum is σ = 20716217492. Its totient is φ = 20716217490.

The previous prime is 20716217447. The next prime is 20716217513. The reversal of 20716217491 is 19471261702.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20716217491 - 2¹⁹ = 20715693203 is a prime.

It is not a weakly prime, because it can be changed into another prime (20716287491) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10358108745 + 10358108746.

It is an arithmetic number, because the mean of its divisors is an integer number (10358108746).

Almost surely, 2^20716217491 is an apocalyptic number.

20716217491 is a deficient number, since it is larger than the sum of its proper divisors (1).

20716217491 is an equidigital number, since it uses as much as digits as its factorization.

20716217491 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 42336, while the sum is 40.

The spelling of 20716217491 in words is "twenty billion, seven hundred sixteen million, two hundred seventeen thousand, four hundred ninety-one".