81403477768 has 8 divisors (see below), whose sum is σ = 152631520830. Its totient is φ = 40701738880.

The previous prime is 81403477733. The next prime is 81403477769. The reversal of 81403477768 is 86777430418.

It can be written as a sum of positive squares in only one way, i.e., 59742114084 + 21661363684 = 244422^2 + 147178^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is not an unprimeable number, because it can be changed into a prime (81403477769) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5087717353 + ... + 5087717368.

Almost surely, 2^81403477768 is an apocalyptic number.

It is an amenable number.

81403477768 is a deficient number, since it is larger than the sum of its proper divisors (71228043062).

81403477768 is a wasteful number, since it uses less digits than its factorization.

81403477768 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10175434727 (or 10175434723 counting only the distinct ones).

The product of its (nonzero) digits is 6322176, while the sum is 55.

The spelling of 81403477768 in words is "eighty-one billion, four hundred three million, four hundred seventy-seven thousand, seven hundred sixty-eight".