130821 has 4 divisors (see below), whose sum is σ = 174432. Its totient is φ = 87212.

The previous prime is 130817. The next prime is 130829. The reversal of 130821 is 128031.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 128031 = 3 ⋅42677.

It is a cyclic number.

It is not a de Polignac number, because 130821 - 2² = 130817 is a prime.

It is a super-2 number, since 2×130821² = 34228268082, which contains 22 as substring.

It is a D-number.

It is a Curzon number.

130821 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 130821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (130829) 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 3 ways as a sum of consecutive naturals, for example, 21801 + ... + 21806.

It is an arithmetic number, because the mean of its divisors is an integer number (43608).

2¹³⁰⁸²¹ is an apocalyptic number.

It is an amenable number.

130821 is a deficient number, since it is larger than the sum of its proper divisors (43611).

130821 is an equidigital number, since it uses as much as digits as its factorization.

130821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 43610.

The product of its (nonzero) digits is 48, while the sum is 15.

The square root of 130821 is about 361.6918578016. The cubic root of 130821 is about 50.7643880031.

Adding to 130821 its reverse (128031), we get a palindrome (258852).

The spelling of 130821 in words is "one hundred thirty thousand, eight hundred twenty-one".