19408421521 has 4 divisors (see below), whose sum is σ = 19932973492. Its totient is φ = 18883869552.

The previous prime is 19408421509. The next prime is 19408421551. The reversal of 19408421521 is 12512480491.

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 15910290496 + 3498131025 = 126136^2 + 59145^2 .

It is a cyclic number.

It is not a de Polignac number, because 19408421521 - 2⁷ = 19408421393 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (37), and also a Moran number because the ratio is a prime number: 524551933 = 19408421521 / (1 + 9 + 4 + 0 + 8 + 4 + 2 + 1 + 5 + 2 + 1).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19408421551) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 262275930 + ... + 262276003.

It is an arithmetic number, because the mean of its divisors is an integer number (4983243373).

Almost surely, 2^19408421521 is an apocalyptic number.

It is an amenable number.

19408421521 is a deficient number, since it is larger than the sum of its proper divisors (524551971).

19408421521 is an equidigital number, since it uses as much as digits as its factorization.

19408421521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 524551970.

The product of its (nonzero) digits is 23040, while the sum is 37.

The spelling of 19408421521 in words is "nineteen billion, four hundred eight million, four hundred twenty-one thousand, five hundred twenty-one".