9991716421 has 2 divisors, whose sum is σ = 9991716422. Its totient is φ = 9991716420.

The previous prime is 9991716349. The next prime is 9991716431. The reversal of 9991716421 is 1246171999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 7727289025 + 2264427396 = 87905^2 + 47586^2 .

It is a cyclic number.

It is not a de Polignac number, because 9991716421 - 2¹³ = 9991708229 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9991716431) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4995858210 + 4995858211.

It is an arithmetic number, because the mean of its divisors is an integer number (4995858211).

Almost surely, 2^9991716421 is an apocalyptic number.

It is an amenable number.

9991716421 is a deficient number, since it is larger than the sum of its proper divisors (1).

9991716421 is an equidigital number, since it uses as much as digits as its factorization.

9991716421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 244944, while the sum is 49.

The square root of 9991716421 is about 99958.5735242355. The cubic root of 9991716421 is about 2153.8396446996.

The spelling of 9991716421 in words is "nine billion, nine hundred ninety-one million, seven hundred sixteen thousand, four hundred twenty-one".