9780998891 has 2 divisors, whose sum is σ = 9780998892. Its totient is φ = 9780998890.

The previous prime is 9780998869. The next prime is 9780998893. The reversal of 9780998891 is 1988990879.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 9780998891 - 2³⁰ = 8707257067 is a prime.

Together with 9780998893, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (9780998893) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4890499445 + 4890499446.

It is an arithmetic number, because the mean of its divisors is an integer number (4890499446).

Almost surely, 2^9780998891 is an apocalyptic number.

9780998891 is a deficient number, since it is larger than the sum of its proper divisors (1).

9780998891 is an equidigital number, since it uses as much as digits as its factorization.

9780998891 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 23514624, while the sum is 68.

The square root of 9780998891 is about 98898.9327091046. The cubic root of 9780998891 is about 2138.5910085632.

The spelling of 9780998891 in words is "nine billion, seven hundred eighty million, nine hundred ninety-eight thousand, eight hundred ninety-one".