81507193947 has 16 divisors (see below), whose sum is σ = 127106736000. Its totient is φ = 51478227432.

The previous prime is 81507193907. The next prime is 81507194017. The reversal of 81507193947 is 74939170518.

It is a happy number.

81507193947 is a `hidden beast` number, since 8 + 1 + 507 + 1 + 93 + 9 + 47 = 666.

It is not a de Polignac number, because 81507193947 - 2³⁰ = 80433452123 is a prime.

It is a super-2 number, since 2×81507193947² (a number of 23 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 81507193893 and 81507193902.

It is not an unprimeable number, because it can be changed into a prime (81507193907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 79441197 + ... + 79442222.

It is an arithmetic number, because the mean of its divisors is an integer number (7944171000).

Almost surely, 2^81507193947 is an apocalyptic number.

81507193947 is a deficient number, since it is larger than the sum of its proper divisors (45599542053).

81507193947 is a wasteful number, since it uses less digits than its factorization.

81507193947 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 158883447 (or 158883441 counting only the distinct ones).

The product of its (nonzero) digits is 1905120, while the sum is 54.

The spelling of 81507193947 in words is "eighty-one billion, five hundred seven million, one hundred ninety-three thousand, nine hundred forty-seven".