640367993 has 2 divisors, whose sum is σ = 640367994. Its totient is φ = 640367992.

The previous prime is 640367953. The next prime is 640368007. The reversal of 640367993 is 399763046.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 455054224 + 185313769 = 21332^2 + 13613^2 .

It is a cyclic number.

It is not a de Polignac number, because 640367993 - 2¹⁶ = 640302457 is a prime.

It is not a weakly prime, because it can be changed into another prime (640367953) 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 as a sum of consecutive naturals, namely, 320183996 + 320183997.

It is an arithmetic number, because the mean of its divisors is an integer number (320183997).

Almost surely, 2^640367993 is an apocalyptic number.

It is an amenable number.

640367993 is a deficient number, since it is larger than the sum of its proper divisors (1).

640367993 is an equidigital number, since it uses as much as digits as its factorization.

640367993 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 734832, while the sum is 47.

The square root of 640367993 is about 25305.4933364280. The cubic root of 640367993 is about 861.9390145502.

The spelling of 640367993 in words is "six hundred forty million, three hundred sixty-seven thousand, nine hundred ninety-three".