21018600 has 72 divisors (see below), whose sum is σ = 70593510. Its totient is φ = 5604480.

The previous prime is 21018563. The next prime is 21018601. The reversal of 21018600 is 681012.

It can be written as a sum of positive squares in 3 ways, for example, as 18714276 + 2304324 = 4326^2 + 1518^2 .

It is a tau number, because it is divible by the number of its divisors (72).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21018601) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 4039 + ... + 7638.

Almost surely, 2^21018600 is an apocalyptic number.

21018600 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21018600 is an abundant number, since it is smaller than the sum of its proper divisors (49574910).

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

21018600 is a wasteful number, since it uses less digits than its factorization.

21018600 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11699 (or 11687 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 18.

The square root of 21018600 is about 4584.6046721609. The cubic root of 21018600 is about 275.9738475535.

Adding to 21018600 its reverse (681012), we get a palindrome (21699612).

It can be divided in two parts, 2101 and 8600, that added together give a palindrome (10701).

The spelling of 21018600 in words is "twenty-one million, eighteen thousand, six hundred".