998721 has 6 divisors (see below), whose sum is σ = 1442610. Its totient is φ = 665808.

The previous prime is 998717. The next prime is 998737. The reversal of 998721 is 127899.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 680625 + 318096 = 825^2 + 564^2 .

It is not a de Polignac number, because 998721 - 2² = 998717 is a prime.

It is a nialpdrome in base 10.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 998721.

It is not an unprimeable number, because it can be changed into a prime (999721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 55476 + ... + 55493.

It is an arithmetic number, because the mean of its divisors is an integer number (240435).

2⁹⁹⁸⁷²¹ is an apocalyptic number.

It is an amenable number.

998721 is a deficient number, since it is larger than the sum of its proper divisors (443889).

998721 is a wasteful number, since it uses less digits than its factorization.

998721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 110975 (or 110972 counting only the distinct ones).

The product of its digits is 9072, while the sum is 36.

The square root of 998721 is about 999.3602953890. The cubic root of 998721 is about 99.9573484777.

The spelling of 998721 in words is "nine hundred ninety-eight thousand, seven hundred twenty-one".