21502 has 8 divisors (see below), whose sum is σ = 34776. Its totient is φ = 9912.

The previous prime is 21499. The next prime is 21503. The reversal of 21502 is 20512.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21503) 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, 388 + ... + 439.

It is an arithmetic number, because the mean of its divisors is an integer number (4347).

2²¹⁵⁰² is an apocalyptic number.

21502 is a deficient number, since it is larger than the sum of its proper divisors (13274).

21502 is a wasteful number, since it uses less digits than its factorization.

21502 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 842.

The product of its (nonzero) digits is 20, while the sum is 10.

The square root of 21502 is about 146.6356027710. The cubic root of 21502 is about 27.8073510226.

Adding to 21502 its sum of digits (10), we get a palindrome (21512).

Subtracting from 21502 its reverse (20512), we obtain a triangular number (990 = T₄₄).

The spelling of 21502 in words is "twenty-one thousand, five hundred two".