6425643661 has 2 divisors, whose sum is σ = 6425643662. Its totient is φ = 6425643660.

The previous prime is 6425643659. The next prime is 6425643667. The reversal of 6425643661 is 1663465246.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 4597653636 + 1827990025 = 67806^2 + 42755^2 .

It is a cyclic number.

It is not a de Polignac number, because 6425643661 - 2¹ = 6425643659 is a prime.

Together with 6425643659, 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 (6425643667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3212821830 + 3212821831.

It is an arithmetic number, because the mean of its divisors is an integer number (3212821831).

Almost surely, 2^6425643661 is an apocalyptic number.

It is an amenable number.

6425643661 is a deficient number, since it is larger than the sum of its proper divisors (1).

6425643661 is an equidigital number, since it uses as much as digits as its factorization.

6425643661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 622080, while the sum is 43.

The square root of 6425643661 is about 80160.1126558590. The cubic root of 6425643661 is about 1859.1119648974. Note that the first 3 decimals are identical.

The spelling of 6425643661 in words is "six billion, four hundred twenty-five million, six hundred forty-three thousand, six hundred sixty-one".