21580056 has 24 divisors (see below), whose sum is σ = 58446180. Its totient is φ = 7193328.

The previous prime is 21580051. The next prime is 21580057. The reversal of 21580056 is 65008512.

It is a tau number, because it is divible by the number of its divisors (24).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21580051) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 149790 + ... + 149933.

Almost surely, 2^21580056 is an apocalyptic number.

It is an amenable number.

21580056 is an abundant number, since it is smaller than the sum of its proper divisors (36866124).

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

21580056 is a wasteful number, since it uses less digits than its factorization.

21580056 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 299735 (or 299728 counting only the distinct ones).

The product of its (nonzero) digits is 2400, while the sum is 27.

The square root of 21580056 is about 4645.4338871627. The cubic root of 21580056 is about 278.4095889484.

Adding to 21580056 its reverse (65008512), we get a palindrome (86588568).

The spelling of 21580056 in words is "twenty-one million, five hundred eighty thousand, fifty-six".