21099600 has 90 divisors (see below), whose sum is σ = 73233966. Its totient is φ = 5625600.

The previous prime is 21099593. The next prime is 21099613. The reversal of 21099600 is 699012.

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 1065024 + 20034576 = 1032^2 + 4476^2 .

It is a tau number, because it is divible by the number of its divisors (90).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 670 + ... + 6530.

Almost surely, 2^21099600 is an apocalyptic number.

21099600 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 21099600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36616983).

21099600 is an abundant number, since it is smaller than the sum of its proper divisors (52134366).

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

21099600 is a wasteful number, since it uses less digits than its factorization.

21099600 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5885 (or 5871 counting only the distinct ones).

The product of its (nonzero) digits is 972, while the sum is 27.

The square root of 21099600 is about 4593.4300909016. The cubic root of 21099600 is about 276.3279026555.

The spelling of 21099600 in words is "twenty-one million, ninety-nine thousand, six hundred".