30821 has 12 divisors (see below), whose sum is σ = 38988. Its totient is φ = 24192.

The previous prime is 30817. The next prime is 30829. The reversal of 30821 is 12803.

30821 = T₆ + T₇ + ... + T₅₆.

It can be written as a sum of positive squares in 2 ways, for example, as 25921 + 4900 = 161^2 + 70^2 .

It is not a de Polignac number, because 30821 - 2² = 30817 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 30796 and 30805.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (30829) 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, 815 + ... + 851.

It is an arithmetic number, because the mean of its divisors is an integer number (3249).

2³⁰⁸²¹ is an apocalyptic number.

It is an amenable number.

30821 is a deficient number, since it is larger than the sum of its proper divisors (8167).

30821 is a wasteful number, since it uses less digits than its factorization.

30821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 68 (or 61 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 14.

The square root of 30821 is about 175.5591068558. The cubic root of 30821 is about 31.3532266409.

The spelling of 30821 in words is "thirty thousand, eight hundred twenty-one".