1644645773 has 4 divisors (see below), whose sum is σ = 1741389660. Its totient is φ = 1547901888.

The previous prime is 1644645763. The next prime is 1644645787. The reversal of 1644645773 is 3775464461.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 3775464461 = 89 ⋅42420949.

It can be written as a sum of positive squares in 2 ways, for example, as 1488570724 + 156075049 = 38582^2 + 12493^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1644645773 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1644645733) 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, 48371918 + ... + 48371951.

It is an arithmetic number, because the mean of its divisors is an integer number (435347415).

Almost surely, 2^1644645773 is an apocalyptic number.

It is an amenable number.

1644645773 is a deficient number, since it is larger than the sum of its proper divisors (96743887).

1644645773 is an equidigital number, since it uses as much as digits as its factorization.

1644645773 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 96743886.

The product of its digits is 1693440, while the sum is 47.

The square root of 1644645773 is about 40554.2324918127. The cubic root of 1644645773 is about 1180.3862024665.

The spelling of 1644645773 in words is "one billion, six hundred forty-four million, six hundred forty-five thousand, seven hundred seventy-three".