21281700 has 72 divisors (see below), whose sum is σ = 67183200. Its totient is φ = 5158400.

The previous prime is 21281683. The next prime is 21281707. The reversal of 21281700 is 718212.

It is not an unprimeable number, because it can be changed into a prime (21281707) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 76 + ... + 6524.

It is an arithmetic number, because the mean of its divisors is an integer number (933100).

Almost surely, 2^21281700 is an apocalyptic number.

21281700 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 21281700, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33591600).

21281700 is an abundant number, since it is smaller than the sum of its proper divisors (45901500).

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

21281700 is a wasteful number, since it uses less digits than its factorization.

21281700 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6477 (or 6470 counting only the distinct ones).

The product of its (nonzero) digits is 224, while the sum is 21.

The square root of 21281700 is about 4613.2092950570. The cubic root of 21281700 is about 277.1205755181.

Adding to 21281700 its reverse (718212), we get a palindrome (21999912).

It can be divided in two parts, 2128 and 1700, that added together give a triangular number (3828 = T₈₇).

The spelling of 21281700 in words is "twenty-one million, two hundred eighty-one thousand, seven hundred".