81669388509 has 16 divisors (see below), whose sum is σ = 128108845440. Its totient is φ = 51243537600.

The previous prime is 81669388487. The next prime is 81669388513. The reversal of 81669388509 is 90588396618.

It is not a de Polignac number, because 81669388509 - 2¹⁵ = 81669355741 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81669389509) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 88964017 + ... + 88964934.

It is an arithmetic number, because the mean of its divisors is an integer number (8006802840).

Almost surely, 2^81669388509 is an apocalyptic number.

It is an amenable number.

81669388509 is a deficient number, since it is larger than the sum of its proper divisors (46439456931).

81669388509 is a wasteful number, since it uses less digits than its factorization.

81669388509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 177928977 (or 177928971 counting only the distinct ones).

The product of its (nonzero) digits is 22394880, while the sum is 63.

The spelling of 81669388509 in words is "eighty-one billion, six hundred sixty-nine million, three hundred eighty-eight thousand, five hundred nine".