21204100 has 36 divisors (see below), whose sum is σ = 48723444. Its totient is φ = 7982080.

The previous prime is 21204077. The next prime is 21204107. The reversal of 21204100 is 140212.

It can be written as a sum of positive squares in 6 ways, for example, as 246016 + 20958084 = 496^2 + 4578^2 .

It is a super-2 number, since 2×21204100² = 899227713620000, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (10).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21204107) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4537 + ... + 7936.

It is an arithmetic number, because the mean of its divisors is an integer number (1353429).

Almost surely, 2^21204100 is an apocalyptic number.

21204100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21204100 is an abundant number, since it is smaller than the sum of its proper divisors (27519344).

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

21204100 is a wasteful number, since it uses less digits than its factorization.

21204100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12504 (or 12497 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 10.

The square root of 21204100 is about 4604.7909833129. The cubic root of 21204100 is about 276.7833413800.

Adding to 21204100 its reverse (140212), we get a palindrome (21344312).

The spelling of 21204100 in words is "twenty-one million, two hundred four thousand, one hundred".