641646409 has 2 divisors, whose sum is σ = 641646410. Its totient is φ = 641646408.

The previous prime is 641646391. The next prime is 641646413. The reversal of 641646409 is 904646146.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 528862009 + 112784400 = 22997^2 + 10620^2 .

It is a cyclic number.

It is not a de Polignac number, because 641646409 - 2¹¹ = 641644361 is a prime.

It is a super-2 number, since 2×641646409² = 823420228365190562, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (641646469) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320823204 + 320823205.

It is an arithmetic number, because the mean of its divisors is an integer number (320823205).

Almost surely, 2^641646409 is an apocalyptic number.

It is an amenable number.

641646409 is a deficient number, since it is larger than the sum of its proper divisors (1).

641646409 is an equidigital number, since it uses as much as digits as its factorization.

641646409 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 124416, while the sum is 40.

The square root of 641646409 is about 25330.7403958116. The cubic root of 641646409 is about 862.5122183804.

It can be divided in two parts, 6416 and 46409, that added together give a palindrome (52825).

The spelling of 641646409 in words is "six hundred forty-one million, six hundred forty-six thousand, four hundred nine".