20509351680 has 144 divisors (see below), whose sum is σ = 66576301344. Its totient is φ = 5379440640.

The previous prime is 20509351613. The next prime is 20509351691. The reversal of 20509351680 is 8615390502.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 190462 + ... + 278018.

It is an arithmetic number, because the mean of its divisors is an integer number (462335426).

Almost surely, 2^20509351680 is an apocalyptic number.

20509351680 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 20509351680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33288150672).

20509351680 is an abundant number, since it is smaller than the sum of its proper divisors (46066949664).

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

20509351680 is an equidigital number, since it uses as much as digits as its factorization.

20509351680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 87642 (or 87628 counting only the distinct ones).

The product of its (nonzero) digits is 64800, while the sum is 39.

The spelling of 20509351680 in words is "twenty billion, five hundred nine million, three hundred fifty-one thousand, six hundred eighty".