21545320 has 32 divisors (see below), whose sum is σ = 48966120. Its totient is φ = 8531200.

The previous prime is 21545311. The next prime is 21545327. The reversal of 21545320 is 2354512.

21545320 = 172² + 173² + ... + 411².

It can be written as a sum of positive squares in 4 ways, for example, as 20738916 + 806404 = 4554^2 + 898^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21545291 and 21545300.

It is not an unprimeable number, because it can be changed into a prime (21545327) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1374 + ... + 6706.

Almost surely, 2^21545320 is an apocalyptic number.

21545320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21545320 is an abundant number, since it is smaller than the sum of its proper divisors (27420800).

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

21545320 is a wasteful number, since it uses less digits than its factorization.

21545320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5445 (or 5441 counting only the distinct ones).

The product of its (nonzero) digits is 1200, while the sum is 22.

The square root of 21545320 is about 4641.6936564146. The cubic root of 21545320 is about 278.2601295129.

Adding to 21545320 its reverse (2354512), we get a palindrome (23899832).

The spelling of 21545320 in words is "twenty-one million, five hundred forty-five thousand, three hundred twenty".