9991421641 has 2 divisors, whose sum is σ = 9991421642. Its totient is φ = 9991421640.

The previous prime is 9991421581. The next prime is 9991421647. The reversal of 9991421641 is 1461241999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 7461331641 + 2530090000 = 86379^2 + 50300^2 .

It is a cyclic number.

It is not a de Polignac number, because 9991421641 - 2¹¹ = 9991419593 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 9991421591 and 9991421600.

It is not a weakly prime, because it can be changed into another prime (9991421647) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4995710820 + 4995710821.

It is an arithmetic number, because the mean of its divisors is an integer number (4995710821).

Almost surely, 2^9991421641 is an apocalyptic number.

It is an amenable number.

9991421641 is a deficient number, since it is larger than the sum of its proper divisors (1).

9991421641 is an equidigital number, since it uses as much as digits as its factorization.

9991421641 is an evil number, because the sum of its binary digits is even.

The product of its digits is 139968, while the sum is 46.

The square root of 9991421641 is about 99957.0990025221. The cubic root of 9991421641 is about 2153.8184633174.

The spelling of 9991421641 in words is "nine billion, nine hundred ninety-one million, four hundred twenty-one thousand, six hundred forty-one".