21609960 has 64 divisors (see below), whose sum is σ = 65508480. Its totient is φ = 5702400.

The previous prime is 21609953. The next prime is 21609977. The reversal of 21609960 is 6990612.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11229 + ... + 13011.

It is an arithmetic number, because the mean of its divisors is an integer number (1023570).

Almost surely, 2^21609960 is an apocalyptic number.

21609960 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 21609960, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32754240).

21609960 is an abundant number, since it is smaller than the sum of its proper divisors (43898520).

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

21609960 is a wasteful number, since it uses less digits than its factorization.

21609960 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1898 (or 1894 counting only the distinct ones).

The product of its (nonzero) digits is 5832, while the sum is 33.

The square root of 21609960 is about 4648.6514173468. The cubic root of 21609960 is about 278.5381292027.

The spelling of 21609960 in words is "twenty-one million, six hundred nine thousand, nine hundred sixty".