641581 has 2 divisors, whose sum is σ = 641582. Its totient is φ = 641580.

The previous prime is 641579. The next prime is 641623. The reversal of 641581 is 185146.

641581 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 443556 + 198025 = 666^2 + 445^2 .

It is a cyclic number.

It is not a de Polignac number, because 641581 - 2¹ = 641579 is a prime.

It is a super-4 number, since 4×641581⁴ (a number of 24 digits) contains 4444 as substring. Note that it is a super-d number also for d = 2.

Together with 641579, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (641521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320790 + 320791.

It is an arithmetic number, because the mean of its divisors is an integer number (320791).

2⁶⁴¹⁵⁸¹ is an apocalyptic number.

It is an amenable number.

641581 is a deficient number, since it is larger than the sum of its proper divisors (1).

641581 is an equidigital number, since it uses as much as digits as its factorization.

641581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 960, while the sum is 25.

The square root of 641581 is about 800.9875155082. The cubic root of 641581 is about 86.2482909414.

The spelling of 641581 in words is "six hundred forty-one thousand, five hundred eighty-one".