645643808041 has 4 divisors (see below), whose sum is σ = 645645435732. Its totient is φ = 645642180352.

The previous prime is 645643808011. The next prime is 645643808057. The reversal of 645643808041 is 140808346546.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 528129225625 + 117514582416 = 726725^2 + 342804^2 .

It is a cyclic number.

It is not a de Polignac number, because 645643808041 - 2¹⁷ = 645643676969 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (645643808011) 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, 213081 + ... + 1156153.

It is an arithmetic number, because the mean of its divisors is an integer number (161411358933).

Almost surely, 2^645643808041 is an apocalyptic number.

It is an amenable number.

645643808041 is a deficient number, since it is larger than the sum of its proper divisors (1627691).

645643808041 is an equidigital number, since it uses as much as digits as its factorization.

645643808041 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1627690.

The product of its (nonzero) digits is 2211840, while the sum is 49.

The spelling of 645643808041 in words is "six hundred forty-five billion, six hundred forty-three million, eight hundred eight thousand, forty-one".