81953765781 has 16 divisors (see below), whose sum is σ = 110522206080. Its totient is φ = 54010837760.

The previous prime is 81953765759. The next prime is 81953765837. The reversal of 81953765781 is 18756735918.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 81953765781 - 2⁹ = 81953765269 is a prime.

It is a super-2 number, since 2×81953765781² (a number of 23 digits) contains 22 as substring.

It is a Smith number, since the sum of its digits (60) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81953765701) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1386961 + ... + 1444841.

It is an arithmetic number, because the mean of its divisors is an integer number (6907637880).

Almost surely, 2^81953765781 is an apocalyptic number.

It is an amenable number.

81953765781 is a deficient number, since it is larger than the sum of its proper divisors (28568440299).

81953765781 is a wasteful number, since it uses less digits than its factorization.

81953765781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 63276.

The product of its digits is 12700800, while the sum is 60.

The spelling of 81953765781 in words is "eighty-one billion, nine hundred fifty-three million, seven hundred sixty-five thousand, seven hundred eighty-one".