21505056 has 24 divisors (see below), whose sum is σ = 56451024. Its totient is φ = 7168320.

The previous prime is 21505039. The next prime is 21505063. The reversal of 21505056 is 65050512.

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

It is a Harshad number since it is a multiple of its sum of digits (24).

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 111910 + ... + 112101.

It is an arithmetic number, because the mean of its divisors is an integer number (2352126).

Almost surely, 2^21505056 is an apocalyptic number.

It is an amenable number.

21505056 is an abundant number, since it is smaller than the sum of its proper divisors (34945968).

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

21505056 is a wasteful number, since it uses less digits than its factorization.

21505056 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 224024 (or 224016 counting only the distinct ones).

The product of its (nonzero) digits is 1500, while the sum is 24.

The square root of 21505056 is about 4637.3544182001. The cubic root of 21505056 is about 278.0866834561.

Adding to 21505056 its reverse (65050512), we get a palindrome (86555568).

The spelling of 21505056 in words is "twenty-one million, five hundred five thousand, fifty-six".