21308400 has 120 divisors (see below), whose sum is σ = 75880560. Its totient is φ = 5679360.

The previous prime is 21308393. The next prime is 21308431. The reversal of 21308400 is 480312.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (120).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 9814 + ... + 11786.

It is an arithmetic number, because the mean of its divisors is an integer number (632338).

Almost surely, 2^21308400 is an apocalyptic number.

21308400 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 21308400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37940280).

21308400 is an abundant number, since it is smaller than the sum of its proper divisors (54572160).

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

21308400 is a wasteful number, since it uses less digits than its factorization.

21308400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2000 (or 1983 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 18.

The square root of 21308400 is about 4616.1022519004. The cubic root of 21308400 is about 277.2364188203.

Adding to 21308400 its reverse (480312), we get a palindrome (21788712).

The spelling of 21308400 in words is "twenty-one million, three hundred eight thousand, four hundred".