640978937 has 2 divisors, whose sum is σ = 640978938. Its totient is φ = 640978936.

The previous prime is 640978907. The next prime is 640978957. The reversal of 640978937 is 739879046.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 336685801 + 304293136 = 18349^2 + 17444^2 .

It is a cyclic number.

It is not a de Polignac number, because 640978937 - 2¹⁸ = 640716793 is a prime.

It is not a weakly prime, because it can be changed into another prime (640978907) 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, 320489468 + 320489469.

It is an arithmetic number, because the mean of its divisors is an integer number (320489469).

Almost surely, 2^640978937 is an apocalyptic number.

It is an amenable number.

640978937 is a deficient number, since it is larger than the sum of its proper divisors (1).

640978937 is an equidigital number, since it uses as much as digits as its factorization.

640978937 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2286144, while the sum is 53.

The square root of 640978937 is about 25317.5618296865. The cubic root of 640978937 is about 862.2130388076.

The spelling of 640978937 in words is "six hundred forty million, nine hundred seventy-eight thousand, nine hundred thirty-seven".