640400902085 has 12 divisors (see below), whose sum is σ = 893947382028. Its totient is φ = 439132046976.

The previous prime is 640400902069. The next prime is 640400902087. The reversal of 640400902085 is 580209004046.

It can be written as a sum of positive squares in 2 ways, for example, as 336439441156 + 303961460929 = 580034^2 + 551327^2 .

It is not a de Polignac number, because 640400902085 - 2⁴ = 640400902069 is a prime.

It is a super-2 number, since 2×640400902085² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640400902087) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1306940372 + ... + 1306940861.

It is an arithmetic number, because the mean of its divisors is an integer number (74495615169).

Almost surely, 2^640400902085 is an apocalyptic number.

It is an amenable number.

640400902085 is a deficient number, since it is larger than the sum of its proper divisors (253546479943).

640400902085 is a wasteful number, since it uses less digits than its factorization.

640400902085 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2613881252 (or 2613881245 counting only the distinct ones).

The product of its (nonzero) digits is 69120, while the sum is 38.

The spelling of 640400902085 in words is "six hundred forty billion, four hundred million, nine hundred two thousand, eighty-five".