21009600 has 126 divisors (see below), whose sum is σ = 74724260. Its totient is φ = 5598720.

The previous prime is 21009587. The next prime is 21009613. The reversal of 21009600 is 690012.

It is an interprime number because it is at equal distance from previous prime (21009587) and next prime (21009613).

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 13671 + ... + 15129.

Almost surely, 2^21009600 is an apocalyptic number.

21009600 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 21009600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37362130).

21009600 is an abundant number, since it is smaller than the sum of its proper divisors (53714660).

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

21009600 is a wasteful number, since it uses less digits than its factorization.

21009600 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1487 (or 1469 counting only the distinct ones).

The product of its (nonzero) digits is 108, while the sum is 18.

The square root of 21009600 is about 4583.6230211482. The cubic root of 21009600 is about 275.9344519829.

Adding to 21009600 its reverse (690012), we get a palindrome (21699612).

It can be divided in two parts, 21009 and 600, that added together give a square (21609 = 147²).

The spelling of 21009600 in words is "twenty-one million, nine thousand, six hundred".