811918643 has 2 divisors, whose sum is σ = 811918644. Its totient is φ = 811918642.

The previous prime is 811918633. The next prime is 811918649. The reversal of 811918643 is 346819118.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 811918643 - 2¹² = 811914547 is a prime.

It is a super-2 number, since 2×811918643² = 1318423765701922898, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 811918643.

It is not a weakly prime, because it can be changed into another prime (811918649) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 405959321 + 405959322.

It is an arithmetic number, because the mean of its divisors is an integer number (405959322).

Almost surely, 2^811918643 is an apocalyptic number.

811918643 is a deficient number, since it is larger than the sum of its proper divisors (1).

811918643 is an equidigital number, since it uses as much as digits as its factorization.

811918643 is an evil number, because the sum of its binary digits is even.

The product of its digits is 41472, while the sum is 41.

The square root of 811918643 is about 28494.1861262960. The cubic root of 811918643 is about 932.9051800523.

It can be divided in two parts, 8119 and 18643, that added together give a palindrome (26762).

The spelling of 811918643 in words is "eight hundred eleven million, nine hundred eighteen thousand, six hundred forty-three".