640647061 has 2 divisors, whose sum is σ = 640647062. Its totient is φ = 640647060.

The previous prime is 640647041. The next prime is 640647079. The reversal of 640647061 is 160746046.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 639584100 + 1062961 = 25290^2 + 1031^2 .

It is a cyclic number.

It is not a de Polignac number, because 640647061 - 2⁷ = 640646933 is a prime.

It is equal to p_33332497 and since 640647061 and 33332497 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640647031) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320323530 + 320323531.

It is an arithmetic number, because the mean of its divisors is an integer number (320323531).

Almost surely, 2^640647061 is an apocalyptic number.

It is an amenable number.

640647061 is a deficient number, since it is larger than the sum of its proper divisors (1).

640647061 is an equidigital number, since it uses as much as digits as its factorization.

640647061 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 24192, while the sum is 34.

The square root of 640647061 is about 25311.0067164465. The cubic root of 640647061 is about 862.0642054124.

The spelling of 640647061 in words is "six hundred forty million, six hundred forty-seven thousand, sixty-one".