21208100 has 18 divisors (see below), whose sum is σ = 46021794. Its totient is φ = 8483200.

The previous prime is 21208097. The next prime is 21208127. The reversal of 21208100 is 180212.

21208100 = T₄₅₅ + T₄₅₆ + ... + T₆₀₄.

It can be written as a sum of positive squares in 3 ways, for example, as 268324 + 20939776 = 518^2 + 4576^2 .

It is a super-2 number, since 2×21208100² = 899567011220000, 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, 105941 + ... + 106140.

Almost surely, 2^21208100 is an apocalyptic number.

21208100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21208100 is an abundant number, since it is smaller than the sum of its proper divisors (24813694).

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

21208100 is a wasteful number, since it uses less digits than its factorization.

21208100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 212095 (or 212088 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 14.

The square root of 21208100 is about 4605.2252930774. The cubic root of 21208100 is about 276.8007446771.

Adding to 21208100 its reverse (180212), we get a palindrome (21388312).

The spelling of 21208100 in words is "twenty-one million, two hundred eight thousand, one hundred".