20661409728 has 336 divisors, whose sum is σ = 62958837760. Its totient is φ = 6469632000.

The previous prime is 20661409651. The next prime is 20661409751. The reversal of 20661409728 is 82790416602.

It is a happy number.

20661409728 is a `hidden beast` number, since 2 + 0 + 6 + 614 + 0 + 9 + 7 + 28 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 136830453 + ... + 136830603.

Almost surely, 2^20661409728 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 20661409728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31479418880).

20661409728 is an abundant number, since it is smaller than the sum of its proper divisors (42297428032).

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

20661409728 is a wasteful number, since it uses less digits than its factorization.

20661409728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 376 (or 363 counting only the distinct ones).

The product of its (nonzero) digits is 290304, while the sum is 45.

The spelling of 20661409728 in words is "twenty billion, six hundred sixty-one million, four hundred nine thousand, seven hundred twenty-eight".