9999766421 has 2 divisors, whose sum is σ = 9999766422. Its totient is φ = 9999766420.

The previous prime is 9999766363. The next prime is 9999766423. The reversal of 9999766421 is 1246679999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 8819088100 + 1180678321 = 93910^2 + 34361^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-9999766421 is a prime.

It is a Sophie Germain prime.

Together with 9999766423, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a nialpdrome in base 10.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9999766423) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4999883210 + 4999883211.

It is an arithmetic number, because the mean of its divisors is an integer number (4999883211).

Almost surely, 2^9999766421 is an apocalyptic number.

It is an amenable number.

9999766421 is a deficient number, since it is larger than the sum of its proper divisors (1).

9999766421 is an equidigital number, since it uses as much as digits as its factorization.

9999766421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 13226976, while the sum is 62.

The square root of 9999766421 is about 99998.8320981800. The cubic root of 9999766421 is about 2154.4179155446.

The spelling of 9999766421 in words is "nine billion, nine hundred ninety-nine million, seven hundred sixty-six thousand, four hundred twenty-one".