97821 has 8 divisors (see below), whose sum is σ = 144960. Its totient is φ = 65196.

The previous prime is 97813. The next prime is 97829. The reversal of 97821 is 12879.

It is an interprime number because it is at equal distance from previous prime (97813) and next prime (97829).

It is not a de Polignac number, because 97821 - 2³ = 97813 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 3623 = 97821 / (9 + 7 + 8 + 2 + 1).

97821 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (97829) 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 7 ways as a sum of consecutive naturals, for example, 1785 + ... + 1838.

It is an arithmetic number, because the mean of its divisors is an integer number (18120).

2⁹⁷⁸²¹ is an apocalyptic number.

It is an amenable number.

97821 is a deficient number, since it is larger than the sum of its proper divisors (47139).

97821 is a wasteful number, since it uses less digits than its factorization.

97821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3632 (or 3626 counting only the distinct ones).

The product of its digits is 1008, while the sum is 27.

The square root of 97821 is about 312.7634889177. The cubic root of 97821 is about 46.0762754694.

It can be divided in two parts, 978 and 21, that added together give a palindrome (999).

The spelling of 97821 in words is "ninety-seven thousand, eight hundred twenty-one".