640550188738891 has 2 divisors, whose sum is σ = 640550188738892. Its totient is φ = 640550188738890.

The previous prime is 640550188738883. The next prime is 640550188738921. The reversal of 640550188738891 is 198837881055046.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 640550188738891 - 2³ = 640550188738883 is a prime.

It is not a weakly prime, because it can be changed into another prime (640550188733891) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320275094369445 + 320275094369446.

It is an arithmetic number, because the mean of its divisors is an integer number (320275094369446).

Almost surely, 2^{640550188738891} is an apocalyptic number.

640550188738891 is a deficient number, since it is larger than the sum of its proper divisors (1).

640550188738891 is an equidigital number, since it uses as much as digits as its factorization.

640550188738891 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 464486400, while the sum is 73.

The spelling of 640550188738891 in words is "six hundred forty trillion, five hundred fifty billion, one hundred eighty-eight million, seven hundred thirty-eight thousand, eight hundred ninety-one".