21601556434640 has 480 divisors, whose sum is σ = 63515234764800. Its totient is φ = 6688343660544.

The previous prime is 21601556434567. The next prime is 21601556434669. The reversal of 21601556434640 is 4643465510612.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 809064011 + ... + 809090709.

It is an arithmetic number, because the mean of its divisors is an integer number (132323405760).

Almost surely, 2^{21601556434640} is an apocalyptic number.

21601556434640 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 21601556434640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31757617382400).

21601556434640 is an abundant number, since it is smaller than the sum of its proper divisors (41913678330160).

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

21601556434640 is a wasteful number, since it uses less digits than its factorization.

21601556434640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26931 (or 26912 counting only the distinct ones).

The product of its (nonzero) digits is 2073600, while the sum is 47.

The spelling of 21601556434640 in words is "twenty-one trillion, six hundred one billion, five hundred fifty-six million, four hundred thirty-four thousand, six hundred forty".