640899855 has 96 divisors (see below), whose sum is σ = 1194298560. Its totient is φ = 317399040.

The previous prime is 640899851. The next prime is 640899869. The reversal of 640899855 is 558998046.

It is a happy number.

It is a Cunningham number, because it is equal to 25316²-1.

It is not a de Polignac number, because 640899855 - 2² = 640899851 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640899851) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 6607167 + ... + 6607263.

It is an arithmetic number, because the mean of its divisors is an integer number (12440610).

Almost surely, 2^640899855 is an apocalyptic number.

640899855 is a deficient number, since it is larger than the sum of its proper divisors (553398705).

640899855 is a wasteful number, since it uses less digits than its factorization.

640899855 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 281 (or 278 counting only the distinct ones).

The product of its (nonzero) digits is 3110400, while the sum is 54.

The square root of 640899855 is about 25315.9999802496. Note that the first 4 decimals coincide. The cubic root of 640899855 is about 862.1775782894.

The spelling of 640899855 in words is "six hundred forty million, eight hundred ninety-nine thousand, eight hundred fifty-five".