21700 has 36 divisors (see below), whose sum is σ = 55552. Its totient is φ = 7200.

The previous prime is 21683. The next prime is 21701. The reversal of 21700 is 712.

21700 = 16³ + 17³ + ... + 19³.

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

It is a plaindrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (21701) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 685 + ... + 715.

2²¹⁷⁰⁰ is an apocalyptic number.

21700 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 21700, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27776).

21700 is an abundant number, since it is smaller than the sum of its proper divisors (33852).

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

21700 is a wasteful number, since it uses less digits than its factorization.

21700 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52 (or 45 counting only the distinct ones).

The product of its (nonzero) digits is 14, while the sum is 10.

The square root of 21700 is about 147.3091986266. The cubic root of 21700 is about 27.8924445226.

The spelling of 21700 in words is "twenty-one thousand, seven hundred", and thus it is an iban number.