997981 has 8 divisors (see below), whose sum is σ = 1036728. Its totient is φ = 960000.

The previous prime is 997973. The next prime is 997991. The reversal of 997981 is 189799.

It can be written as a sum of positive squares in 4 ways, for example, as 260100 + 737881 = 510^2 + 859^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a 5-Lehmer number, since φ(997981) divides (997981-1)⁵.

It is a cyclic number.

It is not a de Polignac number, because 997981 - 2³ = 997973 is a prime.

It is a super-2 number, since 2×997981² = 1991932152722, which contains 22 as substring.

It is a deceptive number, since it divides R₉₉₇₉₈₀.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (997961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4021 + ... + 4261.

It is an arithmetic number, because the mean of its divisors is an integer number (129591).

2⁹⁹⁷⁹⁸¹ is an apocalyptic number.

It is an amenable number.

997981 is a deficient number, since it is larger than the sum of its proper divisors (38747).

997981 is a wasteful number, since it uses less digits than its factorization.

997981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 383.

The product of its digits is 40824, while the sum is 43.

The square root of 997981 is about 998.9899899398. The cubic root of 997981 is about 99.9326546562.

It can be divided in two parts, 99798 and 1, that added together give a palindrome (99799).

The spelling of 997981 in words is "nine hundred ninety-seven thousand, nine hundred eighty-one".