81668768978 has 16 divisors (see below), whose sum is σ = 136536023520. Its totient is φ = 36409605696.

The previous prime is 81668768953. The next prime is 81668769023. The reversal of 81668768978 is 87986786618.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 63210476 + ... + 63211767.

It is an arithmetic number, because the mean of its divisors is an integer number (8533501470).

Almost surely, 2^81668768978 is an apocalyptic number.

81668768978 is a deficient number, since it is larger than the sum of its proper divisors (54867254542).

81668768978 is a wasteful number, since it uses less digits than its factorization.

81668768978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 126422281.

The product of its digits is 390168576, while the sum is 74.

The spelling of 81668768978 in words is "eighty-one billion, six hundred sixty-eight million, seven hundred sixty-eight thousand, nine hundred seventy-eight".