21080520 has 128 divisors (see below), whose sum is σ = 71280000. Its totient is φ = 5541120.

The previous prime is 21080509. The next prime is 21080533. The reversal of 21080520 is 2508012.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21080493 and 21080502.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 141406 + ... + 141554.

It is an arithmetic number, because the mean of its divisors is an integer number (556875).

Almost surely, 2^21080520 is an apocalyptic number.

21080520 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 21080520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35640000).

21080520 is an abundant number, since it is smaller than the sum of its proper divisors (50199480).

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

21080520 is a wasteful number, since it uses less digits than its factorization.

21080520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 300 (or 290 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 18.

The square root of 21080520 is about 4591.3527418398. The cubic root of 21080520 is about 276.2445847031.

Adding to 21080520 its reverse (2508012), we get a palindrome (23588532).

The spelling of 21080520 in words is "twenty-one million, eighty thousand, five hundred twenty".