1643864 has 8 divisors (see below), whose sum is σ = 3082260. Its totient is φ = 821928.

The previous prime is 1643857. The next prime is 1643867. The reversal of 1643864 is 4683461.

1643864 = 313² + 314² + ... + 328².

It is a tau number, because it is divible by the number of its divisors (8).

It is an Ulam number.

It is a self number, because there is not a number n which added to its sum of digits gives 1643864.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1643867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102734 + ... + 102749.

2^1643864 is an apocalyptic number.

It is an amenable number.

1643864 is a deficient number, since it is larger than the sum of its proper divisors (1438396).

1643864 is a wasteful number, since it uses less digits than its factorization.

1643864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 205489 (or 205485 counting only the distinct ones).

The product of its digits is 13824, while the sum is 32.

The square root of 1643864 is about 1282.1325984468. The cubic root of 1643864 is about 118.0199142872.

The spelling of 1643864 in words is "one million, six hundred forty-three thousand, eight hundred sixty-four".