81788719 has 4 divisors (see below), whose sum is σ = 81822096. Its totient is φ = 81755344.

The previous prime is 81788701. The next prime is 81788741. The reversal of 81788719 is 91788718.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81788719 - 2⁷ = 81788591 is a prime.

It is a super-2 number, since 2×81788719² = 13378789111321922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81780719) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12694 + ... + 18019.

It is an arithmetic number, because the mean of its divisors is an integer number (20455524).

Almost surely, 2^81788719 is an apocalyptic number.

81788719 is a deficient number, since it is larger than the sum of its proper divisors (33377).

81788719 is a wasteful number, since it uses less digits than its factorization.

81788719 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33376.

The product of its digits is 225792, while the sum is 49.

The square root of 81788719 is about 9043.7115721367. The cubic root of 81788719 is about 434.0746949664.

Subtracting 81788719 from its reverse (91788718), we obtain a palindrome (9999999).

The spelling of 81788719 in words is "eighty-one million, seven hundred eighty-eight thousand, seven hundred nineteen".