81636942545 has 8 divisors (see below), whose sum is σ = 97965901224. Its totient is φ = 65308507264.

The previous prime is 81636942511. The next prime is 81636942559. The reversal of 81636942545 is 54524963618.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 6657907216 + 74979035329 = 81596^2 + 273823^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81636942545 - 2³⁶ = 12917465809 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 433877 + ... + 592893.

It is an arithmetic number, because the mean of its divisors is an integer number (12245737653).

Almost surely, 2^81636942545 is an apocalyptic number.

It is an amenable number.

81636942545 is a deficient number, since it is larger than the sum of its proper divisors (16328958679).

81636942545 is a wasteful number, since it uses less digits than its factorization.

81636942545 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 261699.

The product of its digits is 6220800, while the sum is 53.

The spelling of 81636942545 in words is "eighty-one billion, six hundred thirty-six million, nine hundred forty-two thousand, five hundred forty-five".