81899819 has 2 divisors, whose sum is σ = 81899820. Its totient is φ = 81899818.

The previous prime is 81899809. The next prime is 81899827. The reversal of 81899819 is 91899818.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81899819 is a prime.

It is a super-2 number, since 2×81899819² = 13415160704465522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81899809) 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 as a sum of consecutive naturals, namely, 40949909 + 40949910.

It is an arithmetic number, because the mean of its divisors is an integer number (40949910).

Almost surely, 2^81899819 is an apocalyptic number.

81899819 is a deficient number, since it is larger than the sum of its proper divisors (1).

81899819 is an equidigital number, since it uses as much as digits as its factorization.

81899819 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 373248, while the sum is 53.

The square root of 81899819 is about 9049.8518772409. The cubic root of 81899819 is about 434.2711518838.

Subtracting 81899819 from its reverse (91899818), we obtain a palindrome (9999999).

The spelling of 81899819 in words is "eighty-one million, eight hundred ninety-nine thousand, eight hundred nineteen".