641507561 has 2 divisors, whose sum is σ = 641507562. Its totient is φ = 641507560.

The previous prime is 641507551. The next prime is 641507593. The reversal of 641507561 is 165705146.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 622801936 + 18705625 = 24956^2 + 4325^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-641507561 is a prime.

It is not a weakly prime, because it can be changed into another prime (641507501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320753780 + 320753781.

It is an arithmetic number, because the mean of its divisors is an integer number (320753781).

Almost surely, 2^641507561 is an apocalyptic number.

It is an amenable number.

641507561 is a deficient number, since it is larger than the sum of its proper divisors (1).

641507561 is an equidigital number, since it uses as much as digits as its factorization.

641507561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 25200, while the sum is 35.

The square root of 641507561 is about 25327.9995459570. Note that the first 3 decimals coincide. The cubic root of 641507561 is about 862.4499999300.

The spelling of 641507561 in words is "six hundred forty-one million, five hundred seven thousand, five hundred sixty-one".