81989779 has 8 divisors (see below), whose sum is σ = 85699872. Its totient is φ = 78291840.

The previous prime is 81989771. The next prime is 81989801. The reversal of 81989779 is 97798918.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81989779 - 2³ = 81989771 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81989771) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12507 + ... + 17899.

It is an arithmetic number, because the mean of its divisors is an integer number (10712484).

Almost surely, 2^81989779 is an apocalyptic number.

81989779 is a deficient number, since it is larger than the sum of its proper divisors (3710093).

81989779 is a wasteful number, since it uses less digits than its factorization.

81989779 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6077.

The product of its digits is 2286144, while the sum is 58.

The square root of 81989779 is about 9054.8207602360. The cubic root of 81989779 is about 434.4300970361.

The spelling of 81989779 in words is "eighty-one million, nine hundred eighty-nine thousand, seven hundred seventy-nine".