21335680 has 128 divisors (see below), whose sum is σ = 56512080. Its totient is φ = 7667712.

The previous prime is 21335647. The next prime is 21335683. The reversal of 21335680 is 8653312.

It can be written as a sum of positive squares in 8 ways, for example, as 18593344 + 2742336 = 4312^2 + 1656^2 .

It is a tau number, because it is divible by the number of its divisors (128).

It is a super-2 number, since 2×21335680² = 910422482124800, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21335683) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 402534 + ... + 402586.

Almost surely, 2^21335680 is an apocalyptic number.

21335680 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 21335680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28256040).

21335680 is an abundant number, since it is smaller than the sum of its proper divisors (35176400).

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

21335680 is a wasteful number, since it uses less digits than its factorization.

21335680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 126 (or 114 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 28.

The square root of 21335680 is about 4619.0561806499. The cubic root of 21335680 is about 277.3546786661.

Adding to 21335680 its reverse (8653312), we get a palindrome (29988992).

The spelling of 21335680 in words is "twenty-one million, three hundred thirty-five thousand, six hundred eighty".