21543400 has 24 divisors (see below), whose sum is σ = 50088870. Its totient is φ = 8617280.

The previous prime is 21543373. The next prime is 21543407. The reversal of 21543400 is 434512.

It can be written as a sum of positive squares in 3 ways, for example, as 13557124 + 7986276 = 3682^2 + 2826^2 .

It is not an unprimeable number, because it can be changed into a prime (21543407) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 53659 + ... + 54058.

Almost surely, 2^21543400 is an apocalyptic number.

21543400 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21543400 is an abundant number, since it is smaller than the sum of its proper divisors (28545470).

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

21543400 is a wasteful number, since it uses less digits than its factorization.

21543400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 107733 (or 107724 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 19.

The square root of 21543400 is about 4641.4868307472. The cubic root of 21543400 is about 278.2518635984.

Adding to 21543400 its reverse (434512), we get a palindrome (21977912).

The spelling of 21543400 in words is "twenty-one million, five hundred forty-three thousand, four hundred".