640267809 has 8 divisors (see below), whose sum is σ = 855208992. Its totient is φ = 426085920.

The previous prime is 640267799. The next prime is 640267811. The reversal of 640267809 is 908762046.

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

It is not a de Polignac number, because 640267809 - 2⁹ = 640267297 is a prime.

It is not an unprimeable number, because it can be changed into a prime (640267009) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 187852 + ... + 191229.

It is an arithmetic number, because the mean of its divisors is an integer number (106901124).

Almost surely, 2^640267809 is an apocalyptic number.

It is an amenable number.

640267809 is a deficient number, since it is larger than the sum of its proper divisors (214941183).

640267809 is a wasteful number, since it uses less digits than its factorization.

640267809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 379647.

The product of its (nonzero) digits is 145152, while the sum is 42.

The square root of 640267809 is about 25303.5137678545. The cubic root of 640267809 is about 861.8940627918.

The spelling of 640267809 in words is "six hundred forty million, two hundred sixty-seven thousand, eight hundred nine".