640656461 has 2 divisors, whose sum is σ = 640656462. Its totient is φ = 640656460.

The previous prime is 640656451. The next prime is 640656463. The reversal of 640656461 is 164656046.

640656461 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 569776900 + 70879561 = 23870^2 + 8419^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-640656461 is a prime.

Together with 640656463, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640656463) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320328230 + 320328231.

It is an arithmetic number, because the mean of its divisors is an integer number (320328231).

Almost surely, 2^640656461 is an apocalyptic number.

It is an amenable number.

640656461 is a deficient number, since it is larger than the sum of its proper divisors (1).

640656461 is an equidigital number, since it uses as much as digits as its factorization.

640656461 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 103680, while the sum is 38.

The square root of 640656461 is about 25311.1924057323. The cubic root of 640656461 is about 862.0684216517.

The spelling of 640656461 in words is "six hundred forty million, six hundred fifty-six thousand, four hundred sixty-one".