21508480 has 64 divisors (see below), whose sum is σ = 58776480. Its totient is φ = 7372800.

The previous prime is 21508439. The next prime is 21508481. The reversal of 21508480 is 8480512.

It is a tau number, because it is divible by the number of its divisors (64).

It is a super-2 number, since 2×21508480² = 925229423820800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21508481) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2080 + ... + 6880.

Almost surely, 2^21508480 is an apocalyptic number.

21508480 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 21508480, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29388240).

21508480 is an abundant number, since it is smaller than the sum of its proper divisors (37268000).

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

21508480 is an equidigital number, since it uses as much as digits as its factorization.

21508480 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4827 (or 4815 counting only the distinct ones).

The product of its (nonzero) digits is 2560, while the sum is 28.

The square root of 21508480 is about 4637.7235795161. The cubic root of 21508480 is about 278.1014415091.

Adding to 21508480 its reverse (8480512), we get a palindrome (29988992).

The spelling of 21508480 in words is "twenty-one million, five hundred eight thousand, four hundred eighty".