1643449618 has 4 divisors (see below), whose sum is σ = 2465174430. Its totient is φ = 821724808.

The previous prime is 1643449607. The next prime is 1643449651. The reversal of 1643449618 is 8169443461.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 8169443461 = 7723 ⋅1057807.

It can be written as a sum of positive squares in only one way, i.e., 1313555049 + 329894569 = 36243^2 + 18163^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410862403 + ... + 410862406.

Almost surely, 2^1643449618 is an apocalyptic number.

1643449618 is a deficient number, since it is larger than the sum of its proper divisors (821724812).

1643449618 is an equidigital number, since it uses as much as digits as its factorization.

1643449618 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 821724811.

The product of its digits is 497664, while the sum is 46.

The square root of 1643449618 is about 40539.4822117895. The cubic root of 1643449618 is about 1180.0999671125.

The spelling of 1643449618 in words is "one billion, six hundred forty-three million, four hundred forty-nine thousand, six hundred eighteen".