21405400 has 96 divisors (see below), whose sum is σ = 54014400. Its totient is φ = 7862400.

The previous prime is 21405383. The next prime is 21405401. The reversal of 21405400 is 450412.

It is a super-2 number, since 2×21405400² = 916382298320000, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21405401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 163335 + ... + 163465.

It is an arithmetic number, because the mean of its divisors is an integer number (562650).

Almost surely, 2^21405400 is an apocalyptic number.

21405400 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 21405400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27007200).

21405400 is an abundant number, since it is smaller than the sum of its proper divisors (32609000).

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

21405400 is a wasteful number, since it uses less digits than its factorization.

21405400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 209 (or 200 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 16.

The square root of 21405400 is about 4626.5970215700. The cubic root of 21405400 is about 277.6564602083.

Adding to 21405400 its reverse (450412), we get a palindrome (21855812).

The spelling of 21405400 in words is "twenty-one million, four hundred five thousand, four hundred".