21615554434440 has 256 divisors, whose sum is σ = 66387744218880. Its totient is φ = 5628958617600.

The previous prime is 21615554434399. The next prime is 21615554434613. The reversal of 21615554434440 is 4443445551612.

It is a super-2 number, since 2×21615554434440² (a number of 27 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 21615554434440.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 616635954 + ... + 616671006.

It is an arithmetic number, because the mean of its divisors is an integer number (259327125855).

Almost surely, 2^{21615554434440} is an apocalyptic number.

21615554434440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21615554434440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33193872109440).

21615554434440 is an abundant number, since it is smaller than the sum of its proper divisors (44772189784440).

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

21615554434440 is a wasteful number, since it uses less digits than its factorization.

21615554434440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35864 (or 35860 counting only the distinct ones).

The product of its (nonzero) digits is 4608000, while the sum is 48.

The spelling of 21615554434440 in words is "twenty-one trillion, six hundred fifteen billion, five hundred fifty-four million, four hundred thirty-four thousand, four hundred forty".