21525540 has 96 divisors (see below), whose sum is σ = 63504000. Its totient is φ = 5440512.

The previous prime is 21525529. The next prime is 21525541. The reversal of 21525540 is 4552512.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21525540.

It is not an unprimeable number, because it can be changed into a prime (21525541) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 154791 + ... + 154929.

It is an arithmetic number, because the mean of its divisors is an integer number (661500).

Almost surely, 2^21525540 is an apocalyptic number.

21525540 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 21525540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31752000).

21525540 is an abundant number, since it is smaller than the sum of its proper divisors (41978460).

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

21525540 is a wasteful number, since it uses less digits than its factorization.

21525540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 269 (or 267 counting only the distinct ones).

The product of its (nonzero) digits is 2000, while the sum is 24.

The square root of 21525540 is about 4639.5624793724. The cubic root of 21525540 is about 278.1749498302.

The spelling of 21525540 in words is "twenty-one million, five hundred twenty-five thousand, five hundred forty".