21540900 has 72 divisors (see below), whose sum is σ = 63433440. Its totient is φ = 5642240.

The previous prime is 21540863. The next prime is 21540901. The reversal of 21540900 is 904512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21540901) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 17092 + ... + 18308.

It is an arithmetic number, because the mean of its divisors is an integer number (881020).

Almost surely, 2^21540900 is an apocalyptic number.

21540900 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 21540900, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31716720).

21540900 is an abundant number, since it is smaller than the sum of its proper divisors (41892540).

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

21540900 is a wasteful number, since it uses less digits than its factorization.

21540900 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1293 (or 1286 counting only the distinct ones).

The product of its (nonzero) digits is 360, while the sum is 21.

The square root of 21540900 is about 4641.2175126792. The cubic root of 21540900 is about 278.2410999527.

The spelling of 21540900 in words is "twenty-one million, five hundred forty thousand, nine hundred".