81668069817 has 4 divisors (see below), whose sum is σ = 108890759760. Its totient is φ = 54445379876.

The previous prime is 81668069809. The next prime is 81668069839. The reversal of 81668069817 is 71896086618.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81668069817 - 2³ = 81668069809 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81660069817) 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, 13611344967 + ... + 13611344972.

It is an arithmetic number, because the mean of its divisors is an integer number (27222689940).

Almost surely, 2^81668069817 is an apocalyptic number.

It is an amenable number.

81668069817 is a deficient number, since it is larger than the sum of its proper divisors (27222689943).

81668069817 is a wasteful number, since it uses less digits than its factorization.

81668069817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27222689942.

The product of its (nonzero) digits is 6967296, while the sum is 60.

The spelling of 81668069817 in words is "eighty-one billion, six hundred sixty-eight million, sixty-nine thousand, eight hundred seventeen".