21520080 has 180 divisors, whose sum is σ = 76877892. Its totient is φ = 5598720.

The previous prime is 21520069. The next prime is 21520091. The reversal of 21520080 is 8002512.

21520080 is a nontrivial binomial coefficient, being equal to C(6561, 2).

It is an interprime number because it is at equal distance from previous prime (21520069) and next prime (21520091).

It can be written as a sum of positive squares in 2 ways, for example, as 3779136 + 17740944 = 1944^2 + 4212^2 .

It is a tau number, because it is divible by the number of its divisors (180).

It is a super-2 number, since 2×21520080² = 926227686412800, which contains 22 as substring.

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

It is a nialpdrome in base 3 and base 9.

It is a zygodrome in base 3 and base 9.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 524860 + ... + 524900.

Almost surely, 2^21520080 is an apocalyptic number.

21520080 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

21520080 is the 6560-th triangular number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21520080, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38438946).

21520080 is an abundant number, since it is smaller than the sum of its proper divisors (55357812).

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

21520080 is an frugal number, since it uses more digits than its factorization.

21520080 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 78 (or 51 counting only the distinct ones).

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

The square root of 21520080 is about 4638.9740245015. The cubic root of 21520080 is about 278.1514279478.

Adding to 21520080 its reverse (8002512), we get a palindrome (29522592).

The spelling of 21520080 in words is "twenty-one million, five hundred twenty thousand, eighty".