21724056 has 48 divisors (see below), whose sum is σ = 60740160. Its totient is φ = 7007040.

The previous prime is 21724037. The next prime is 21724057. The reversal of 21724056 is 65042712.

It is a super-2 number, since 2×21724056² = 943869218182272, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21724057) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2635 + ... + 7098.

It is an arithmetic number, because the mean of its divisors is an integer number (1265420).

Almost surely, 2^21724056 is an apocalyptic number.

It is an amenable number.

21724056 is an abundant number, since it is smaller than the sum of its proper divisors (39016104).

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

21724056 is a wasteful number, since it uses less digits than its factorization.

21724056 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9776 (or 9769 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 27.

The square root of 21724056 is about 4660.9072078298. The cubic root of 21724056 is about 279.0274763860.

Adding to 21724056 its reverse (65042712), we get a palindrome (86766768).

The spelling of 21724056 in words is "twenty-one million, seven hundred twenty-four thousand, fifty-six".