1643975644 has 12 divisors (see below), whose sum is σ = 2877260904. Its totient is φ = 821901104.

The previous prime is 1643975629. The next prime is 1643975659. The reversal of 1643975644 is 4465793461.

It is an interprime number because it is at equal distance from previous prime (1643975629) and next prime (1643975659).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 41307 + ... + 70669.

It is an arithmetic number, because the mean of its divisors is an integer number (239771742).

Almost surely, 2^1643975644 is an apocalyptic number.

It is an amenable number.

1643975644 is a deficient number, since it is larger than the sum of its proper divisors (1233285260).

1643975644 is a wasteful number, since it uses less digits than its factorization.

1643975644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43364 (or 43362 counting only the distinct ones).

The product of its digits is 2177280, while the sum is 49.

The square root of 1643975644 is about 40545.9695160937. The cubic root of 1643975644 is about 1180.2258602420.

The spelling of 1643975644 in words is "one billion, six hundred forty-three million, nine hundred seventy-five thousand, six hundred forty-four".