16581443449 has 4 divisors (see below), whose sum is σ = 16610181364. Its totient is φ = 16552705536.

The previous prime is 16581443413. The next prime is 16581443479. The reversal of 16581443449 is 94434418561.

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 16101833449 + 479610000 = 126893^2 + 21900^2 .

It is a cyclic number.

It is not a de Polignac number, because 16581443449 - 2³³ = 7991508857 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16581443479) 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, 14368092 + ... + 14369245.

It is an arithmetic number, because the mean of its divisors is an integer number (4152545341).

Almost surely, 2^16581443449 is an apocalyptic number.

It is an amenable number.

16581443449 is a deficient number, since it is larger than the sum of its proper divisors (28737915).

16581443449 is an equidigital number, since it uses as much as digits as its factorization.

16581443449 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28737914.

The product of its digits is 1658880, while the sum is 49.

The spelling of 16581443449 in words is "sixteen billion, five hundred eighty-one million, four hundred forty-three thousand, four hundred forty-nine".