9978821 has 2 divisors, whose sum is σ = 9978822. Its totient is φ = 9978820.

The previous prime is 9978817. The next prime is 9978827. The reversal of 9978821 is 1288799.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 5522500 + 4456321 = 2350^2 + 2111^2 .

It is an emirp because it is prime and its reverse (1288799) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 9978821 - 2² = 9978817 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9978827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4989410 + 4989411.

It is an arithmetic number, because the mean of its divisors is an integer number (4989411).

Almost surely, 2^9978821 is an apocalyptic number.

It is an amenable number.

9978821 is a deficient number, since it is larger than the sum of its proper divisors (1).

9978821 is an equidigital number, since it uses as much as digits as its factorization.

9978821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 72576, while the sum is 44.

The square root of 9978821 is about 3158.9271913104. The cubic root of 9978821 is about 215.2912655944.

The spelling of 9978821 in words is "nine million, nine hundred seventy-eight thousand, eight hundred twenty-one".