640657767 has 8 divisors (see below), whose sum is σ = 904458096. Its totient is φ = 401981312.

The previous prime is 640657757. The next prime is 640657781. The reversal of 640657767 is 767756046.

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

It is a cyclic number.

It is not a de Polignac number, because 640657767 - 2²⁶ = 573548903 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640657757) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6280908 + ... + 6281009.

It is an arithmetic number, because the mean of its divisors is an integer number (113057262).

Almost surely, 2^640657767 is an apocalyptic number.

640657767 is a deficient number, since it is larger than the sum of its proper divisors (263800329).

640657767 is a wasteful number, since it uses less digits than its factorization.

640657767 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12561937.

The product of its (nonzero) digits is 1481760, while the sum is 48.

The square root of 640657767 is about 25311.2182045827. The cubic root of 640657767 is about 862.0690074366.

The spelling of 640657767 in words is "six hundred forty million, six hundred fifty-seven thousand, seven hundred sixty-seven".