81660779 has 6 divisors (see below), whose sum is σ = 83071860. Its totient is φ = 80273276.

The previous prime is 81660773. The next prime is 81660797. The reversal of 81660779 is 97706618.

It is a de Polignac number, because none of the positive numbers 2^k-81660779 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81660773) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 8249 + ... + 15210.

It is an arithmetic number, because the mean of its divisors is an integer number (13845310).

Almost surely, 2^81660779 is an apocalyptic number.

81660779 is a deficient number, since it is larger than the sum of its proper divisors (1411081).

81660779 is an equidigital number, since it uses as much as digits as its factorization.

81660779 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23577 (or 23518 counting only the distinct ones).

The product of its (nonzero) digits is 127008, while the sum is 44.

The square root of 81660779 is about 9036.6353804942. The cubic root of 81660779 is about 433.8482395337.

The spelling of 81660779 in words is "eighty-one million, six hundred sixty thousand, seven hundred seventy-nine".