81261159165 has 48 divisors (see below), whose sum is σ = 149326035456. Its totient is φ = 40807670400.

The previous prime is 81261159163. The next prime is 81261159167. The reversal of 81261159165 is 56195116218.

81261159165 is a `hidden beast` number, since 8 + 12 + 611 + 5 + 9 + 16 + 5 = 666.

It is an interprime number because it is at equal distance from previous prime (81261159163) and next prime (81261159167).

It is not a de Polignac number, because 81261159165 - 2¹ = 81261159163 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 81261159165.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81261159163) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 735571 + ... + 838800.

It is an arithmetic number, because the mean of its divisors is an integer number (3110959072).

Almost surely, 2^81261159165 is an apocalyptic number.

It is an amenable number.

81261159165 is a deficient number, since it is larger than the sum of its proper divisors (68064876291).

81261159165 is a wasteful number, since it uses less digits than its factorization.

81261159165 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1574450 (or 1574447 counting only the distinct ones).

The product of its digits is 129600, while the sum is 45.

The spelling of 81261159165 in words is "eighty-one billion, two hundred sixty-one million, one hundred fifty-nine thousand, one hundred sixty-five".