640999477 has 2 divisors, whose sum is σ = 640999478. Its totient is φ = 640999476.

The previous prime is 640999459. The next prime is 640999481. The reversal of 640999477 is 774999046.

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., 374461201 + 266538276 = 19351^2 + 16326^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-640999477 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640999417) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320499738 + 320499739.

It is an arithmetic number, because the mean of its divisors is an integer number (320499739).

Almost surely, 2^640999477 is an apocalyptic number.

It is an amenable number.

640999477 is a deficient number, since it is larger than the sum of its proper divisors (1).

640999477 is an equidigital number, since it uses as much as digits as its factorization.

640999477 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3429216, while the sum is 55.

The square root of 640999477 is about 25317.9674737132. The cubic root of 640999477 is about 862.2222485053. Note that the first 4 decimals are identical.

The spelling of 640999477 in words is "six hundred forty million, nine hundred ninety-nine thousand, four hundred seventy-seven".