640877813 has 2 divisors, whose sum is σ = 640877814. Its totient is φ = 640877812.

The previous prime is 640877801. The next prime is 640877821. The reversal of 640877813 is 318778046.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 635392849 + 5484964 = 25207^2 + 2342^2 .

It is a cyclic number.

It is not a de Polignac number, because 640877813 - 2⁸ = 640877557 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640877863) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320438906 + 320438907.

It is an arithmetic number, because the mean of its divisors is an integer number (320438907).

Almost surely, 2^640877813 is an apocalyptic number.

It is an amenable number.

640877813 is a deficient number, since it is larger than the sum of its proper divisors (1).

640877813 is an equidigital number, since it uses as much as digits as its factorization.

640877813 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 225792, while the sum is 44.

The square root of 640877813 is about 25315.5646391701. The cubic root of 640877813 is about 862.1676940951.

The spelling of 640877813 in words is "six hundred forty million, eight hundred seventy-seven thousand, eight hundred thirteen".