21561209484 has 12 divisors (see below), whose sum is σ = 50309488824. Its totient is φ = 7187069824.

The previous prime is 21561209479. The next prime is 21561209491. The reversal of 21561209484 is 48490216512.

It is a tau number, because it is divible by the number of its divisors (12).

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, 898383717 + ... + 898383740.

It is an arithmetic number, because the mean of its divisors is an integer number (4192457402).

Almost surely, 2^21561209484 is an apocalyptic number.

It is an amenable number.

21561209484 is an abundant number, since it is smaller than the sum of its proper divisors (28748279340).

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

21561209484 is a wasteful number, since it uses less digits than its factorization.

21561209484 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1796767464 (or 1796767462 counting only the distinct ones).

The product of its (nonzero) digits is 138240, while the sum is 42.

The spelling of 21561209484 in words is "twenty-one billion, five hundred sixty-one million, two hundred nine thousand, four hundred eighty-four".