640121210856 has 48 divisors (see below), whose sum is σ = 1742461964100. Its totient is φ = 212290616832.

The previous prime is 640121210851. The next prime is 640121210863. The reversal of 640121210856 is 658012121046.

It is a happy number.

640121210856 is a `hidden beast` number, since 640 + 1 + 2 + 1 + 2 + 1 + 0 + 8 + 5 + 6 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 514613977956 + 125507232900 = 717366^2 + 354270^2 .

It is a super-2 number, since 2×640121210856² (a number of 24 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 640121210856.

It is not an unprimeable number, because it can be changed into a prime (640121210851) 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 11 ways as a sum of consecutive naturals, for example, 22550721 + ... + 22579088.

Almost surely, 2^640121210856 is an apocalyptic number.

It is an amenable number.

640121210856 is an abundant number, since it is smaller than the sum of its proper divisors (1102340753244).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

640121210856 is a wasteful number, since it uses less digits than its factorization.

640121210856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45130018 (or 45130011 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 36.

The spelling of 640121210856 in words is "six hundred forty billion, one hundred twenty-one million, two hundred ten thousand, eight hundred fifty-six".