21505005004 has 12 divisors (see below), whose sum is σ = 43010010064. Its totient is φ = 9216430704.

The previous prime is 21505005001. The next prime is 21505005007. The reversal of 21505005004 is 40050050512.

It is an interprime number because it is at equal distance from previous prime (21505005001) and next prime (21505005007).

21505005004 is an admirable number.

It is not an unprimeable number, because it can be changed into a prime (21505005001) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 384017919 + ... + 384017974.

Almost surely, 2^21505005004 is an apocalyptic number.

It is an amenable number.

21505005004 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21505005004 is a wasteful number, since it uses less digits than its factorization.

21505005004 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 768035904 (or 768035902 counting only the distinct ones).

The product of its (nonzero) digits is 1000, while the sum is 22.

Adding to 21505005004 its reverse (40050050512), we get a palindrome (61555055516).

The spelling of 21505005004 in words is "twenty-one billion, five hundred five million, five thousand, four".