21500 has 24 divisors (see below), whose sum is σ = 48048. Its totient is φ = 8400.

The previous prime is 21499. The next prime is 21503. The reversal of 21500 is 512.

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 polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 479 + ... + 521.

It is an arithmetic number, because the mean of its divisors is an integer number (2002).

2²¹⁵⁰⁰ is an apocalyptic number.

21500 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24024).

21500 is an abundant number, since it is smaller than the sum of its proper divisors (26548).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21500 is a wasteful number, since it uses less digits than its factorization.

21500 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 62 (or 50 counting only the distinct ones).

The product of its (nonzero) digits is 10, while the sum is 8.

The square root of 21500 is about 146.6287829862. The cubic root of 21500 is about 27.8064888326.

The spelling of 21500 in words is "twenty-one thousand, five hundred".