640827855 has 40 divisors (see below), whose sum is σ = 1163342400. Its totient is φ = 337431744.

The previous prime is 640827853. The next prime is 640827883. The reversal of 640827855 is 558728046.

It is not a de Polignac number, because 640827855 - 2¹ = 640827853 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 640827855.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640827853) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 21981 + ... + 42009.

It is an arithmetic number, because the mean of its divisors is an integer number (29083560).

Almost surely, 2^640827855 is an apocalyptic number.

640827855 is a deficient number, since it is larger than the sum of its proper divisors (522514545).

640827855 is a wasteful number, since it uses less digits than its factorization.

640827855 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20125 (or 20116 counting only the distinct ones).

The product of its (nonzero) digits is 537600, while the sum is 45.

The square root of 640827855 is about 25314.5779147115. The cubic root of 640827855 is about 862.1452908163.

The spelling of 640827855 in words is "six hundred forty million, eight hundred twenty-seven thousand, eight hundred fifty-five".