21561007104 has 528 divisors, whose sum is σ = 78397283328. Its totient is φ = 5555257344.

The previous prime is 21561007099. The next prime is 21561007121. The reversal of 21561007104 is 40170016512.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 39416559 + ... + 39417105.

Almost surely, 2^21561007104 is an apocalyptic number.

21561007104 is a gapful number since it is divisible by the number (24) 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 21561007104, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39198641664).

21561007104 is an abundant number, since it is smaller than the sum of its proper divisors (56836276224).

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

21561007104 is a wasteful number, since it uses less digits than its factorization.

21561007104 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 640 (or 619 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 27.

The spelling of 21561007104 in words is "twenty-one billion, five hundred sixty-one million, seven thousand, one hundred four".