1643640208 has 40 divisors (see below), whose sum is σ = 3641443520. Its totient is φ = 704039040.

The previous prime is 1643640179. The next prime is 1643640209. The reversal of 1643640208 is 8020463461.

It is not an unprimeable number, because it can be changed into a prime (1643640209) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 335698 + ... + 340558.

It is an arithmetic number, because the mean of its divisors is an integer number (91036088).

Almost surely, 2^1643640208 is an apocalyptic number.

It is an amenable number.

1643640208 is an abundant number, since it is smaller than the sum of its proper divisors (1997803312).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1643640208 is a wasteful number, since it uses less digits than its factorization.

1643640208 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7895 (or 7889 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 34.

The square root of 1643640208 is about 40541.8328150073. The cubic root of 1643640208 is about 1180.1455838762.

It can be divided in two parts, 16436 and 40208, that added together give a square (56644 = 238²).

The spelling of 1643640208 in words is "one billion, six hundred forty-three million, six hundred forty thousand, two hundred eight".