21155961560 has 16 divisors (see below), whose sum is σ = 47600913600. Its totient is φ = 8462384608.

The previous prime is 21155961557. The next prime is 21155961581. The reversal of 21155961560 is 6516955112.

It is a congruent number.

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, 264449480 + ... + 264449559.

It is an arithmetic number, because the mean of its divisors is an integer number (2975057100).

Almost surely, 2^21155961560 is an apocalyptic number.

21155961560 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21155961560 is an abundant number, since it is smaller than the sum of its proper divisors (26444952040).

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

21155961560 is a wasteful number, since it uses less digits than its factorization.

21155961560 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 528899050 (or 528899046 counting only the distinct ones).

The product of its (nonzero) digits is 81000, while the sum is 41.

The spelling of 21155961560 in words is "twenty-one billion, one hundred fifty-five million, nine hundred sixty-one thousand, five hundred sixty".