21251808400 has 135 divisors (see below), whose sum is σ = 52742417889. Its totient is φ = 8228989440.

The previous prime is 21251808377. The next prime is 21251808451. The reversal of 21251808400 is 480815212.

The square root of 21251808400 is 145780.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 13 ways, for example, as 612463504 + 20639344896 = 24748^2 + 143664^2 .

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 107877102 + ... + 107877298.

Almost surely, 2^21251808400 is an apocalyptic number.

21251808400 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

21251808400 is the 145780-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21251808400

21251808400 is an abundant number, since it is smaller than the sum of its proper divisors (31490609489).

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

21251808400 is an equidigital number, since it uses as much as digits as its factorization.

21251808400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 486 (or 241 counting only the distinct ones).

The product of its (nonzero) digits is 5120, while the sum is 31.

The spelling of 21251808400 in words is "twenty-one billion, two hundred fifty-one million, eight hundred eight thousand, four hundred".