21830 has 16 divisors (see below), whose sum is σ = 41040. Its totient is φ = 8352.

The previous prime is 21821. The next prime is 21839. The reversal of 21830 is 3812.

It is an interprime number because it is at equal distance from previous prime (21821) and next prime (21839).

It is an alternating number because its digits alternate between even and odd.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21839) by changing a digit.

21830 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 341 + ... + 399.

It is an arithmetic number, because the mean of its divisors is an integer number (2565).

2²¹⁸³⁰ is an apocalyptic number.

21830 is a deficient number, since it is larger than the sum of its proper divisors (19210).

21830 is a wasteful number, since it uses less digits than its factorization.

21830 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 103.

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

The square root of 21830 is about 147.7497884939. The cubic root of 21830 is about 27.9480328620.

The spelling of 21830 in words is "twenty-one thousand, eight hundred thirty".