21005600 has 216 divisors, whose sum is σ = 66495744. Its totient is φ = 6336000.

The previous prime is 21005597. The next prime is 21005609. The reversal of 21005600 is 650012.

It is a Harshad number since it is a multiple of its sum of digits (14).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21005609) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 677585 + ... + 677615.

Almost surely, 2^21005600 is an apocalyptic number.

21005600 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 21005600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33247872).

21005600 is an abundant number, since it is smaller than the sum of its proper divisors (45490144).

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

21005600 is a wasteful number, since it uses less digits than its factorization.

21005600 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80 (or 56 counting only the distinct ones).

The product of its (nonzero) digits is 60, while the sum is 14.

The square root of 21005600 is about 4583.1866643199. The cubic root of 21005600 is about 275.9169392290.

Adding to 21005600 its reverse (650012), we get a palindrome (21655612).

The spelling of 21005600 in words is "twenty-one million, five thousand, six hundred".