641891 has 2 divisors, whose sum is σ = 641892. Its totient is φ = 641890.

The previous prime is 641881. The next prime is 641897. The reversal of 641891 is 198146.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 641891 - 2⁶ = 641827 is a prime.

It is an Ulam number.

It is not a weakly prime, because it can be changed into another prime (641897) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320945 + 320946.

It is an arithmetic number, because the mean of its divisors is an integer number (320946).

2⁶⁴¹⁸⁹¹ is an apocalyptic number.

641891 is a deficient number, since it is larger than the sum of its proper divisors (1).

641891 is an equidigital number, since it uses as much as digits as its factorization.

641891 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1728, while the sum is 29.

The square root of 641891 is about 801.1810032695. The cubic root of 641891 is about 86.2621798944.

The spelling of 641891 in words is "six hundred forty-one thousand, eight hundred ninety-one".