21709056 has 72 divisors (see below), whose sum is σ = 60338880. Its totient is φ = 6916096.

The previous prime is 21709027. The next prime is 21709063. The reversal of 21709056 is 65090712.

It is a super-3 number, since 3×21709056³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17050 + ... + 18278.

It is an arithmetic number, because the mean of its divisors is an integer number (838040).

Almost surely, 2^21709056 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21709056, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30169440).

21709056 is an abundant number, since it is smaller than the sum of its proper divisors (38629824).

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

21709056 is a wasteful number, since it uses less digits than its factorization.

21709056 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1271 (or 1257 counting only the distinct ones).

The product of its (nonzero) digits is 3780, while the sum is 30.

The square root of 21709056 is about 4659.2978011713. The cubic root of 21709056 is about 278.9632407474.

Adding to 21709056 its reverse (65090712), we get a palindrome (86799768).

The spelling of 21709056 in words is "twenty-one million, seven hundred nine thousand, fifty-six".