21802 has 8 divisors (see below), whose sum is σ = 35712. Its totient is φ = 9900.

The previous prime is 21799. The next prime is 21803. The reversal of 21802 is 20812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (21803) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 474 + ... + 517.

It is an arithmetic number, because the mean of its divisors is an integer number (4464).

2²¹⁸⁰² is an apocalyptic number.

21802 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

21802 is a deficient number, since it is larger than the sum of its proper divisors (13910).

21802 is a wasteful number, since it uses less digits than its factorization.

21802 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1004.

The product of its (nonzero) digits is 32, while the sum is 13.

The square root of 21802 is about 147.6550033016. The cubic root of 21802 is about 27.9360786746.

Subtracting from 21802 its reverse (20812), we obtain a triangular number (990 = T₄₄).

The spelling of 21802 in words is "twenty-one thousand, eight hundred two".