19980785521 has 4 divisors (see below), whose sum is σ = 20308339444. Its totient is φ = 19653231600.

The previous prime is 19980785519. The next prime is 19980785549. The reversal of 19980785521 is 12558708991.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 4545456400 + 15435329121 = 67420^2 + 124239^2 .

It is a cyclic number.

It is not a de Polignac number, because 19980785521 - 2¹ = 19980785519 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19980785581) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 163776870 + ... + 163776991.

It is an arithmetic number, because the mean of its divisors is an integer number (5077084861).

Almost surely, 2^19980785521 is an apocalyptic number.

It is an amenable number.

19980785521 is a deficient number, since it is larger than the sum of its proper divisors (327553923).

19980785521 is an equidigital number, since it uses as much as digits as its factorization.

19980785521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 327553922.

The product of its (nonzero) digits is 1814400, while the sum is 55.

The spelling of 19980785521 in words is "nineteen billion, nine hundred eighty million, seven hundred eighty-five thousand, five hundred twenty-one".