21520005056 has 56 divisors (see below), whose sum is σ = 47577182976. Its totient is φ = 9573681920.

The previous prime is 21520005029. The next prime is 21520005061. The reversal of 21520005056 is 65050002512.

It is a super-2 number, since 2×21520005056² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 292106 + ... + 358281.

Almost surely, 2^21520005056 is an apocalyptic number.

It is an amenable number.

21520005056 is an abundant number, since it is smaller than the sum of its proper divisors (26057177920).

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

21520005056 is a wasteful number, since it uses less digits than its factorization.

21520005056 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 650457 (or 650447 counting only the distinct ones).

The product of its (nonzero) digits is 3000, while the sum is 26.

Adding to 21520005056 its reverse (65050002512), we get a palindrome (86570007568).

The spelling of 21520005056 in words is "twenty-one billion, five hundred twenty million, five thousand, fifty-six".