81817606643 has 2 divisors, whose sum is σ = 81817606644. Its totient is φ = 81817606642.

The previous prime is 81817606573. The next prime is 81817606667. The reversal of 81817606643 is 34660671818.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81817606643 - 2¹⁶ = 81817541107 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 81817606591 and 81817606600.

It is not a weakly prime, because it can be changed into another prime (81817606693) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40908803321 + 40908803322.

It is an arithmetic number, because the mean of its divisors is an integer number (40908803322).

Almost surely, 2^81817606643 is an apocalyptic number.

81817606643 is a deficient number, since it is larger than the sum of its proper divisors (1).

81817606643 is an equidigital number, since it uses as much as digits as its factorization.

81817606643 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1161216, while the sum is 50.

The spelling of 81817606643 in words is "eighty-one billion, eight hundred seventeen million, six hundred six thousand, six hundred forty-three".