21609760 has 48 divisors (see below), whose sum is σ = 51492672. Its totient is φ = 8569600.

The previous prime is 21609733. The next prime is 21609767. The reversal of 21609760 is 6790612.

It is a zygodrome in base 3.

It is not an unprimeable number, because it can be changed into a prime (21609767) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 20445 + ... + 21475.

It is an arithmetic number, because the mean of its divisors is an integer number (1072764).

Almost surely, 2^21609760 is an apocalyptic number.

21609760 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 21609760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25746336).

21609760 is an abundant number, since it is smaller than the sum of its proper divisors (29882912).

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

21609760 is a wasteful number, since it uses less digits than its factorization.

21609760 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1177 (or 1169 counting only the distinct ones).

The product of its (nonzero) digits is 4536, while the sum is 31.

The square root of 21609760 is about 4648.6299056819. The cubic root of 21609760 is about 278.5372699107.

The spelling of 21609760 in words is "twenty-one million, six hundred nine thousand, seven hundred sixty".