643745855971 has 2 divisors, whose sum is σ = 643745855972. Its totient is φ = 643745855970.

The previous prime is 643745855969. The next prime is 643745856041. The reversal of 643745855971 is 179558547346.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 643745855971 - 2¹ = 643745855969 is a prime.

Together with 643745855969, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (643745859971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321872927985 + 321872927986.

It is an arithmetic number, because the mean of its divisors is an integer number (321872927986).

Almost surely, 2^643745855971 is an apocalyptic number.

643745855971 is a deficient number, since it is larger than the sum of its proper divisors (1).

643745855971 is an equidigital number, since it uses as much as digits as its factorization.

643745855971 is an evil number, because the sum of its binary digits is even.

The product of its digits is 127008000, while the sum is 64.

The spelling of 643745855971 in words is "six hundred forty-three billion, seven hundred forty-five million, eight hundred fifty-five thousand, nine hundred seventy-one".