998397781 has 4 divisors (see below), whose sum is σ = 998478412. Its totient is φ = 998317152.

The previous prime is 998397737. The next prime is 998397791. The reversal of 998397781 is 187793899.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 187793899 = 41 ⋅4580339.

It can be written as a sum of positive squares in 2 ways, for example, as 473758756 + 524639025 = 21766^2 + 22905^2 .

It is a cyclic number.

It is not a de Polignac number, because 998397781 - 2¹⁹ = 997873493 is a prime.

It is a super-2 number, since 2×998397781² = 1993596258211447922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (998397721) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 17400 + ... + 47953.

It is an arithmetic number, because the mean of its divisors is an integer number (249619603).

Almost surely, 2^998397781 is an apocalyptic number.

It is an amenable number.

998397781 is a deficient number, since it is larger than the sum of its proper divisors (80631).

998397781 is a wasteful number, since it uses less digits than its factorization.

998397781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80630.

The product of its digits is 6858432, while the sum is 61.

The square root of 998397781 is about 31597.4331394181. The cubic root of 998397781 is about 999.4656415119.

The spelling of 998397781 in words is "nine hundred ninety-eight million, three hundred ninety-seven thousand, seven hundred eighty-one".