81978769 has 8 divisors (see below), whose sum is σ = 84167072. Its totient is φ = 79803360.

The previous prime is 81978761. The next prime is 81978773. The reversal of 81978769 is 96787918.

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 81978769 - 2³ = 81978761 is a prime.

It is a super-2 number, since 2×81978769² = 13441037133510722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81978761) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10414 + ... + 16504.

It is an arithmetic number, because the mean of its divisors is an integer number (10520884).

Almost surely, 2^81978769 is an apocalyptic number.

It is an amenable number.

81978769 is a deficient number, since it is larger than the sum of its proper divisors (2188303).

81978769 is a wasteful number, since it uses less digits than its factorization.

81978769 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6447.

The product of its digits is 1524096, while the sum is 55.

The square root of 81978769 is about 9054.2127763821. The cubic root of 81978769 is about 434.4106503459.

The spelling of 81978769 in words is "eighty-one million, nine hundred seventy-eight thousand, seven hundred sixty-nine".