9991421647 has 2 divisors, whose sum is σ = 9991421648. Its totient is φ = 9991421646.

The previous prime is 9991421641. The next prime is 9991421683. The reversal of 9991421647 is 7461241999.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 9991421647 - 2⁷ = 9991421519 is a prime.

It is a super-3 number, since 3×9991421647³ (a number of 31 digits) contains 333 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 9991421594 and 9991421603.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9991421641) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4995710823 + 4995710824.

It is an arithmetic number, because the mean of its divisors is an integer number (4995710824).

Almost surely, 2^9991421647 is an apocalyptic number.

9991421647 is a deficient number, since it is larger than the sum of its proper divisors (1).

9991421647 is an equidigital number, since it uses as much as digits as its factorization.

9991421647 is an evil number, because the sum of its binary digits is even.

The product of its digits is 979776, while the sum is 52.

The square root of 9991421647 is about 99957.0990325350. The cubic root of 9991421647 is about 2153.8184637485.

The spelling of 9991421647 in words is "nine billion, nine hundred ninety-one million, four hundred twenty-one thousand, six hundred forty-seven".