21288100 has 18 divisors (see below), whose sum is σ = 46195394. Its totient is φ = 8515200.

The previous prime is 21288083. The next prime is 21288119. The reversal of 21288100 is 188212.

It can be written as a sum of positive squares in 3 ways, for example, as 984064 + 20304036 = 992^2 + 4506^2 .

It is a super-2 number, since 2×21288100² = 906366403220000, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 106341 + ... + 106540.

Almost surely, 2^21288100 is an apocalyptic number.

21288100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21288100 is an abundant number, since it is smaller than the sum of its proper divisors (24907294).

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

21288100 is a wasteful number, since it uses less digits than its factorization.

21288100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 212895 (or 212888 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 22.

The square root of 21288100 is about 4613.9029031829. The cubic root of 21288100 is about 277.1483520260.

The spelling of 21288100 in words is "twenty-one million, two hundred eighty-eight thousand, one hundred".