81507038781 has 32 divisors (see below), whose sum is σ = 131660743680. Its totient is φ = 43784522496.

The previous prime is 81507038777. The next prime is 81507038797. The reversal of 81507038781 is 18783070518.

It is a happy number.

It is not a de Polignac number, because 81507038781 - 2² = 81507038777 is a prime.

It is a super-2 number, since 2×81507038781² (a number of 23 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81507038781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81507038581) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 173770 + ... + 439556.

It is an arithmetic number, because the mean of its divisors is an integer number (4114398240).

Almost surely, 2^81507038781 is an apocalyptic number.

It is an amenable number.

81507038781 is a deficient number, since it is larger than the sum of its proper divisors (50153704899).

81507038781 is a wasteful number, since it uses less digits than its factorization.

81507038781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 266673.

The product of its (nonzero) digits is 376320, while the sum is 48.

The spelling of 81507038781 in words is "eighty-one billion, five hundred seven million, thirty-eight thousand, seven hundred eighty-one".