21505535616 has 32 divisors (see below), whose sum is σ = 57124080000. Its totient is φ = 7168511744.

The previous prime is 21505535599. The next prime is 21505535621. The reversal of 21505535616 is 61653550512.

It is a tau number, because it is divible by the number of its divisors (32).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 28001616 + ... + 28002383.

It is an arithmetic number, because the mean of its divisors is an integer number (1785127500).

Almost surely, 2^21505535616 is an apocalyptic number.

It is an amenable number.

21505535616 is an abundant number, since it is smaller than the sum of its proper divisors (35618544384).

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

21505535616 is an equidigital number, since it uses as much as digits as its factorization.

21505535616 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56004016 (or 56004004 counting only the distinct ones).

The product of its (nonzero) digits is 135000, while the sum is 39.

The spelling of 21505535616 in words is "twenty-one billion, five hundred five million, five hundred thirty-five thousand, six hundred sixteen".