21078400 has 96 divisors (see below), whose sum is σ = 59572080. Its totient is φ = 7219200.

The previous prime is 21078371. The next prime is 21078403. The reversal of 21078400 is 487012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21078403) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 21930 + ... + 22870.

Almost surely, 2^21078400 is an apocalyptic number.

21078400 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 21078400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29786040).

21078400 is an abundant number, since it is smaller than the sum of its proper divisors (38493680).

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

21078400 is an equidigital number, since it uses as much as digits as its factorization.

21078400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 972 (or 955 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 22.

The square root of 21078400 is about 4591.1218672564. The cubic root of 21078400 is about 276.2353240499.

The spelling of 21078400 in words is "twenty-one million, seventy-eight thousand, four hundred".