816571643 has 2 divisors, whose sum is σ = 816571644. Its totient is φ = 816571642.

The previous prime is 816571631. The next prime is 816571663. The reversal of 816571643 is 346175618.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 816571643 - 2¹⁸ = 816309499 is a prime.

It is a Sophie Germain prime.

It is a self number, because there is not a number n which added to its sum of digits gives 816571643.

It is not a weakly prime, because it can be changed into another prime (816571603) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 408285821 + 408285822.

It is an arithmetic number, because the mean of its divisors is an integer number (408285822).

Almost surely, 2^816571643 is an apocalyptic number.

816571643 is a deficient number, since it is larger than the sum of its proper divisors (1).

816571643 is an equidigital number, since it uses as much as digits as its factorization.

816571643 is an evil number, because the sum of its binary digits is even.

The product of its digits is 120960, while the sum is 41.

The square root of 816571643 is about 28575.7177162709. The cubic root of 816571643 is about 934.6839058475.

The spelling of 816571643 in words is "eight hundred sixteen million, five hundred seventy-one thousand, six hundred forty-three".