21615554555364 has 576 divisors, whose sum is σ = 67668932701440. Its totient is φ = 5304063098880.

The previous prime is 21615554555359. The next prime is 21615554555389. The reversal of 21615554555364 is 46355545551612.

It is an unprimeable number.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 1230314772 + ... + 1230332340.

It is an arithmetic number, because the mean of its divisors is an integer number (117480785940).

Almost surely, 2^{21615554555364} is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21615554555364, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33834466350720).

21615554555364 is an abundant number, since it is smaller than the sum of its proper divisors (46053378146076).

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

21615554555364 is a wasteful number, since it uses less digits than its factorization.

21615554555364 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17788 (or 17779 counting only the distinct ones).

The product of its digits is 54000000, while the sum is 57.

The spelling of 21615554555364 in words is "twenty-one trillion, six hundred fifteen billion, five hundred fifty-four million, five hundred fifty-five thousand, three hundred sixty-four".