102821 has 4 divisors (see below), whose sum is σ = 103500. Its totient is φ = 102144.

The previous prime is 102811. The next prime is 102829. The reversal of 102821 is 128201.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 81796 + 21025 = 286^2 + 145^2 .

It is a cyclic number.

It is not a de Polignac number, because 102821 - 2¹⁰ = 101797 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 102796 and 102805.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 102821.

It is not an unprimeable number, because it can be changed into a prime (102829) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5 + ... + 453.

It is an arithmetic number, because the mean of its divisors is an integer number (25875).

2¹⁰²⁸²¹ is an apocalyptic number.

It is an amenable number.

102821 is a deficient number, since it is larger than the sum of its proper divisors (679).

102821 is an equidigital number, since it uses as much as digits as its factorization.

102821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 678.

The product of its (nonzero) digits is 32, while the sum is 14.

The square root of 102821 is about 320.6571377656. The cubic root of 102821 is about 46.8483113260.

The spelling of 102821 in words is "one hundred two thousand, eight hundred twenty-one".