21253680 has 120 divisors (see below), whose sum is σ = 81592992. Its totient is φ = 4856832.

The previous prime is 21253667. The next prime is 21253697. The reversal of 21253680 is 8635212.

It is a tau number, because it is divible by the number of its divisors (120).

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2932 + ... + 7148.

Almost surely, 2^21253680 is an apocalyptic number.

21253680 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 21253680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40796496).

21253680 is an abundant number, since it is smaller than the sum of its proper divisors (60339312).

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

21253680 is a wasteful number, since it uses less digits than its factorization.

21253680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4243 (or 4234 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 27.

The square root of 21253680 is about 4610.1713634094. The cubic root of 21253680 is about 276.9989008893.

Adding to 21253680 its reverse (8635212), we get a palindrome (29888892).

The spelling of 21253680 in words is "twenty-one million, two hundred fifty-three thousand, six hundred eighty".