19513016721 has 135 divisors (see below), whose sum is σ = 34450462123. Its totient is φ = 10996318080.

The previous prime is 19513016707. The next prime is 19513016771. The reversal of 19513016721 is 12761031591.

It is a happy number.

The square root of 19513016721 is 139689.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 15191795025 + 4321221696 = 123255^2 + 65736^2 .

It is not a de Polignac number, because 19513016721 - 2⁵ = 19513016689 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (19513016771) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 134 ways as a sum of consecutive naturals, for example, 235096546 + ... + 235096628.

Almost surely, 2^19513016721 is an apocalyptic number.

19513016721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

19513016721 is the 139689-th square number.

19513016721 is the 69845-th centered octagonal number.

It is an amenable number.

19513016721 is a deficient number, since it is larger than the sum of its proper divisors (14937445402).

19513016721 is an equidigital number, since it uses as much as digits as its factorization.

19513016721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 234 (or 114 counting only the distinct ones).

The product of its (nonzero) digits is 11340, while the sum is 36.

Multiplying 19513016721 by its sum of digits (36), we get a square (702468601956 = 838134²).

The spelling of 19513016721 in words is "nineteen billion, five hundred thirteen million, sixteen thousand, seven hundred twenty-one".