21606400 has 78 divisors (see below), whose sum is σ = 53831252. Its totient is φ = 8601600.

The previous prime is 21606359. The next prime is 21606419. The reversal of 21606400 is 460612.

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 5 ways as a sum of consecutive naturals, for example, 102295 + ... + 102505.

Almost surely, 2^21606400 is an apocalyptic number.

21606400 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 21606400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26915626).

21606400 is an abundant number, since it is smaller than the sum of its proper divisors (32224852).

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

21606400 is an equidigital number, since it uses as much as digits as its factorization.

21606400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 245 (or 218 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 19.

The square root of 21606400 is about 4648.2684948269. The cubic root of 21606400 is about 278.5228330122.

It can be divided in two parts, 2160 and 6400, that multiplied together give a cube (13824000 = 240³).

The spelling of 21606400 in words is "twenty-one million, six hundred six thousand, four hundred".