643655645 has 8 divisors (see below), whose sum is σ = 773747640. Its totient is φ = 514017280.

The previous prime is 643655641. The next prime is 643655659. The reversal of 643655645 is 546556346.

It can be written as a sum of positive squares in 4 ways, for example, as 46977316 + 596678329 = 6854^2 + 24427^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 643655645 - 2² = 643655641 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 643655596 and 643655605.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643655641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 110276 + ... + 115965.

It is an arithmetic number, because the mean of its divisors is an integer number (96718455).

Almost surely, 2^643655645 is an apocalyptic number.

It is an amenable number.

643655645 is a deficient number, since it is larger than the sum of its proper divisors (130091995).

643655645 is a wasteful number, since it uses less digits than its factorization.

643655645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 226815.

The product of its digits is 1296000, while the sum is 44.

The square root of 643655645 is about 25370.3694297107. The cubic root of 643655645 is about 863.4115635826.

The spelling of 643655645 in words is "six hundred forty-three million, six hundred fifty-five thousand, six hundred forty-five".