997821 has 12 divisors (see below), whose sum is σ = 1572480. Its totient is φ = 604680.

The previous prime is 997813. The next prime is 997877. The reversal of 997821 is 128799.

It is a happy number.

It is not a de Polignac number, because 997821 - 2³ = 997813 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (997811) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4941 + ... + 5138.

It is an arithmetic number, because the mean of its divisors is an integer number (131040).

2⁹⁹⁷⁸²¹ is an apocalyptic number.

It is an amenable number.

997821 is a deficient number, since it is larger than the sum of its proper divisors (574659).

997821 is a wasteful number, since it uses less digits than its factorization.

997821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10096 (or 10093 counting only the distinct ones).

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

The square root of 997821 is about 998.9099058474. The cubic root of 997821 is about 99.9273138467.

It can be divided in two parts, 9978 and 21, that added together give a palindrome (9999).

The spelling of 997821 in words is "nine hundred ninety-seven thousand, eight hundred twenty-one".