640655434361 has 4 divisors (see below), whose sum is σ = 640784681892. Its totient is φ = 640526186832.

The previous prime is 640655434357. The next prime is 640655434399. The reversal of 640655434361 is 163434556046.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 163434556046 = 2 ⋅81717278023.

It can be written as a sum of positive squares in 2 ways, for example, as 538434555961 + 102220878400 = 733781^2 + 319720^2 .

It is a cyclic number.

It is not a de Polignac number, because 640655434361 - 2² = 640655434357 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640655434301) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64616330 + ... + 64626243.

It is an arithmetic number, because the mean of its divisors is an integer number (160196170473).

Almost surely, 2^640655434361 is an apocalyptic number.

It is an amenable number.

640655434361 is a deficient number, since it is larger than the sum of its proper divisors (129247531).

640655434361 is a wasteful number, since it uses less digits than its factorization.

640655434361 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 129247530.

The product of its (nonzero) digits is 3110400, while the sum is 47.

The spelling of 640655434361 in words is "six hundred forty billion, six hundred fifty-five million, four hundred thirty-four thousand, three hundred sixty-one".