21508265744 has 80 divisors (see below), whose sum is σ = 50857221120. Its totient is φ = 8612835840.

The previous prime is 21508265741. The next prime is 21508265759. The reversal of 21508265744 is 44756280512.

It is a junction number, because it is equal to n+sod(n) for n = 21508265695 and 21508265704.

It is not an unprimeable number, because it can be changed into a prime (21508265741) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6119 + ... + 207494.

It is an arithmetic number, because the mean of its divisors is an integer number (635715264).

Almost surely, 2^21508265744 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 21508265744, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25428610560).

21508265744 is an abundant number, since it is smaller than the sum of its proper divisors (29348955376).

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

21508265744 is a wasteful number, since it uses less digits than its factorization.

21508265744 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 213688 (or 213682 counting only the distinct ones).

The product of its (nonzero) digits is 537600, while the sum is 44.

The spelling of 21508265744 in words is "twenty-one billion, five hundred eight million, two hundred sixty-five thousand, seven hundred forty-four".