81811819 has 16 divisors (see below), whose sum is σ = 85962240. Its totient is φ = 77798880.

The previous prime is 81811817. The next prime is 81811831. The reversal of 81811819 is 91811818.

It is a cyclic number.

It is not a de Polignac number, because 81811819 - 2¹ = 81811817 is a prime.

It is a super-2 number, since 2×81811819² = 13386347456177522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81811811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 451909 + ... + 452089.

It is an arithmetic number, because the mean of its divisors is an integer number (5372640).

Almost surely, 2^81811819 is an apocalyptic number.

81811819 is a deficient number, since it is larger than the sum of its proper divisors (4150421).

81811819 is a wasteful number, since it uses less digits than its factorization.

81811819 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 450.

The product of its digits is 4608, while the sum is 37.

The square root of 81811819 is about 9044.9886124859. The cubic root of 81811819 is about 434.1155570874.

Subtracting 81811819 from its reverse (91811818), we obtain a palindrome (9999999).

It can be divided in two parts, 8181 and 1819, that added together give a 4-th power (10000 = 10⁴).

The spelling of 81811819 in words is "eighty-one million, eight hundred eleven thousand, eight hundred nineteen".