678640731809 has 4 divisors (see below), whose sum is σ = 684646402116.
Its totient is φ = 672635061504.
The previous prime is 678640731803. The next prime is 678640731827. The reversal of 678640731809 is 908137046876.
It is a semiprime because it is the product of two primes.
It can be written as a sum of positive squares in 2 ways, for example, as 180306390625 + 498334341184 = 424625^2 + 705928^2
It is a cyclic number.
It is not a de Polignac number, because 678640731809 - 232 = 674345764513 is a prime.
It is a Duffinian number.
It is a Curzon number.
It is not an unprimeable number, because it can be changed into a prime (678640731803) 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, 3002834984 + ... + 3002835209.
It is an arithmetic number, because the mean of its divisors is an integer number (171161600529).
Almost surely, 2678640731809 is an apocalyptic number.
It is an amenable number.
678640731809 is a deficient number, since it is larger than the sum of its proper divisors (6005670307).
678640731809 is a wasteful number, since it uses less digits than its factorization.
678640731809 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 6005670306.
The product of its (nonzero) digits is 12192768, while the sum is 59.
The spelling of 678640731809 in words is "six hundred seventy-eight billion, six hundred forty million, seven hundred thirty-one thousand, eight hundred nine".