998709781 has 2 divisors, whose sum is σ = 998709782. Its totient is φ = 998709780.

The previous prime is 998709779. The next prime is 998709823. The reversal of 998709781 is 187907899.

998709781 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 891918225 + 106791556 = 29865^2 + 10334^2 .

It is a cyclic number.

It is not a de Polignac number, because 998709781 - 2¹ = 998709779 is a prime.

It is a super-2 number, since 2×998709781² = 1994842453330135922, which contains 22 as substring.

Together with 998709779, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (998709181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499354890 + 499354891.

It is an arithmetic number, because the mean of its divisors is an integer number (499354891).

Almost surely, 2^998709781 is an apocalyptic number.

It is an amenable number.

998709781 is a deficient number, since it is larger than the sum of its proper divisors (1).

998709781 is an equidigital number, since it uses as much as digits as its factorization.

998709781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2286144, while the sum is 58.

The square root of 998709781 is about 31602.3698636669. The cubic root of 998709781 is about 999.5697419045.

The spelling of 998709781 in words is "nine hundred ninety-eight million, seven hundred nine thousand, seven hundred eighty-one".