21605117884 has 48 divisors (see below), whose sum is σ = 43597128960. Its totient is φ = 9176618880.

The previous prime is 21605117861. The next prime is 21605117893. The reversal of 21605117884 is 48871150612.

It is a super-2 number, since 2×21605117884² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21605117884.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3147384 + ... + 3154240.

It is an arithmetic number, because the mean of its divisors is an integer number (908273520).

Almost surely, 2^21605117884 is an apocalyptic number.

It is an amenable number.

21605117884 is an abundant number, since it is smaller than the sum of its proper divisors (21992011076).

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

21605117884 is a wasteful number, since it uses less digits than its factorization.

21605117884 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7858 (or 7856 counting only the distinct ones).

The product of its (nonzero) digits is 107520, while the sum is 43.

The spelling of 21605117884 in words is "twenty-one billion, six hundred five million, one hundred seventeen thousand, eight hundred eighty-four".