997991281 has 9 divisors (see below), whose sum is σ = 1161185931.
Its totient is φ = 855231552.
The previous prime is 997991263. The next prime is 997991287. The reversal of 997991281 is 182199799.
The square root of 997991281 is 31591.
It is a perfect power (a square), and thus also a powerful number.
It can be written as a sum of positive squares in only one way, i.e., 442225 + 997549056 = 665^2 + 31584^2
It is not a de Polignac number, because 997991281 - 221 = 995894129 is a prime.
It is a super-2 number, since 2×9979912812 = 1991973193904041922, which contains 22 as substring.
It is a Duffinian number.
It is not an unprimeable number, because it can be changed into a prime (997991287) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (17) of ones.
It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 218881 + ... + 223393.
It is an arithmetic number, because the mean of its divisors is an integer number (129020659).
Almost surely, 2997991281 is an apocalyptic number.
997991281 is the 31591-st square number.
997991281 is the 15796-th centered octagonal number.
It is an amenable number.
997991281 is a deficient number, since it is larger than the sum of its proper divisors (163194650).
997991281 is an frugal number, since it uses more digits than its factorization.
997991281 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 9040 (or 4520 counting only the distinct ones).
The product of its digits is 734832, while the sum is 55.
The cubic root of 997991281 is about 999.3299781710.
The spelling of 997991281 in words is "nine hundred ninety-seven million, nine hundred ninety-one thousand, two hundred eighty-one".