21278400 has 336 divisors, whose sum is σ = 84661248. Its totient is φ = 4608000.

The previous prime is 21278399. The next prime is 21278401. The reversal of 21278400 is 487212.

It is an interprime number because it is at equal distance from previous prime (21278399) and next prime (21278401).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21278401) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 686385 + ... + 686415.

It is an arithmetic number, because the mean of its divisors is an integer number (251968).

Almost surely, 2^21278400 is an apocalyptic number.

21278400 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 21278400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42330624).

21278400 is an abundant number, since it is smaller than the sum of its proper divisors (63382848).

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

21278400 is a wasteful number, since it uses less digits than its factorization.

21278400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80 (or 65 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 24.

The square root of 21278400 is about 4612.8516126145. The cubic root of 21278400 is about 277.1062510802.

The spelling of 21278400 in words is "twenty-one million, two hundred seventy-eight thousand, four hundred".