21505634628 has 24 divisors (see below), whose sum is σ = 50216722080. Its totient is φ = 7163272320.

The previous prime is 21505634621. The next prime is 21505634651. The reversal of 21505634628 is 82643650512.

It is a self number, because there is not a number n which added to its sum of digits gives 21505634628.

It is not an unprimeable number, because it can be changed into a prime (21505634621) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 642058 + ... + 674721.

It is an arithmetic number, because the mean of its divisors is an integer number (2092363420).

Almost surely, 2^21505634628 is an apocalyptic number.

It is an amenable number.

21505634628 is an abundant number, since it is smaller than the sum of its proper divisors (28711087452).

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

21505634628 is a wasteful number, since it uses less digits than its factorization.

21505634628 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1318147 (or 1318145 counting only the distinct ones).

The product of its (nonzero) digits is 345600, while the sum is 42.

The spelling of 21505634628 in words is "twenty-one billion, five hundred five million, six hundred thirty-four thousand, six hundred twenty-eight".