81294973568 has 16 divisors (see below), whose sum is σ = 161954830410. Its totient is φ = 40647486720.

The previous prime is 81294973549. The next prime is 81294973741. The reversal of 81294973568 is 86537949218.

It can be written as a sum of positive squares in only one way, i.e., 55435760704 + 25859212864 = 235448^2 + 160808^2 .

It is a tau number, because it is divible by the number of its divisors (16).

It is a self number, because there is not a number n which added to its sum of digits gives 81294973568.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 317558363 + ... + 317558618.

Almost surely, 2^81294973568 is an apocalyptic number.

It is an amenable number.

81294973568 is a deficient number, since it is larger than the sum of its proper divisors (80659856842).

81294973568 is an equidigital number, since it uses as much as digits as its factorization.

81294973568 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 635116995 (or 635116983 counting only the distinct ones).

The product of its digits is 26127360, while the sum is 62.

The spelling of 81294973568 in words is "eighty-one billion, two hundred ninety-four million, nine hundred seventy-three thousand, five hundred sixty-eight".