21609056 has 24 divisors (see below), whose sum is σ = 48620880. Its totient is φ = 9260928.

The previous prime is 21609053. The next prime is 21609083. The reversal of 21609056 is 65090612.

It is a super-2 number, since 2×21609056² = 933902602422272, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21609053) 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 3 ways as a sum of consecutive naturals, for example, 48011 + ... + 48458.

It is an arithmetic number, because the mean of its divisors is an integer number (2025870).

Almost surely, 2^21609056 is an apocalyptic number.

It is an amenable number.

21609056 is an abundant number, since it is smaller than the sum of its proper divisors (27011824).

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

21609056 is an equidigital number, since it uses as much as digits as its factorization.

21609056 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 96486 (or 96478 counting only the distinct ones).

The product of its (nonzero) digits is 3240, while the sum is 29.

The square root of 21609056 is about 4648.5541838296. The cubic root of 21609056 is about 278.5342451607.

Adding to 21609056 its reverse (65090612), we get a palindrome (86699668).

The spelling of 21609056 in words is "twenty-one million, six hundred nine thousand, fifty-six".