21729740640 has 384 divisors, whose sum is σ = 73899786240. Its totient is φ = 5350883328.

The previous prime is 21729740639. The next prime is 21729740699. The reversal of 21729740640 is 4604792712.

It is a junction number, because it is equal to n+sod(n) for n = 21729740592 and 21729740601.

It is a congruent number.

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, 84551392 + ... + 84551648.

It is an arithmetic number, because the mean of its divisors is an integer number (192447360).

Almost surely, 2^21729740640 is an apocalyptic number.

21729740640 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 21729740640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36949893120).

21729740640 is an abundant number, since it is smaller than the sum of its proper divisors (52170045600).

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

21729740640 is a wasteful number, since it uses less digits than its factorization.

21729740640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 494 (or 486 counting only the distinct ones).

The product of its (nonzero) digits is 169344, while the sum is 42.

The spelling of 21729740640 in words is "twenty-one billion, seven hundred twenty-nine million, seven hundred forty thousand, six hundred forty".