21250 has 20 divisors (see below), whose sum is σ = 42174. Its totient is φ = 8000.

The previous prime is 21247. The next prime is 21269. The reversal of 21250 is 5212.

21250 is an esthetic number in base 13, because in such base its adjacent digits differ by 1.

It can be written as a sum of positive squares in 5 ways, for example, as 1369 + 19881 = 37^2 + 141^2 .

It is a Harshad number since it is a multiple of its sum of digits (10).

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

21250 is an undulating number in base 13.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 1242 + ... + 1258.

2²¹²⁵⁰ is an apocalyptic number.

21250 is a deficient number, since it is larger than the sum of its proper divisors (20924).

21250 is an equidigital number, since it uses as much as digits as its factorization.

21250 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39 (or 24 counting only the distinct ones).

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

The square root of 21250 is about 145.7737973711. The cubic root of 21250 is about 27.6982912838.

Adding to 21250 its reverse (5212), we get a palindrome (26462).

It can be divided in two parts, 212 and 50, that added together give a palindrome (262).

The spelling of 21250 in words is "twenty-one thousand, two hundred fifty".