6405819781 has 2 divisors, whose sum is σ = 6405819782. Its totient is φ = 6405819780.

The previous prime is 6405819743. The next prime is 6405819799. The reversal of 6405819781 is 1879185046.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 5738062500 + 667757281 = 75750^2 + 25841^2 .

It is a cyclic number.

It is not a de Polignac number, because 6405819781 - 2⁷ = 6405819653 is a prime.

It is a super-2 number, since 2×6405819781² = 82069054133301775922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6405819481) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3202909890 + 3202909891.

It is an arithmetic number, because the mean of its divisors is an integer number (3202909891).

Almost surely, 2^6405819781 is an apocalyptic number.

It is an amenable number.

6405819781 is a deficient number, since it is larger than the sum of its proper divisors (1).

6405819781 is an equidigital number, since it uses as much as digits as its factorization.

6405819781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 483840, while the sum is 49.

The square root of 6405819781 is about 80036.3653660010. The cubic root of 6405819781 is about 1857.1981344164.

The spelling of 6405819781 in words is "six billion, four hundred five million, eight hundred nineteen thousand, seven hundred eighty-one".