72665761681 has 4 divisors (see below), whose sum is σ = 72704810164. Its totient is φ = 72626713200.

The previous prime is 72665761657. The next prime is 72665761717. The reversal of 72665761681 is 18616756627.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 32712148225 + 39953613456 = 180865^2 + 199884^2 .

It is a cyclic number.

It is not a de Polignac number, because 72665761681 - 2²¹ = 72663664529 is a prime.

It is a super-2 number, since 2×72665761681² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (72665761631) 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 3 ways as a sum of consecutive naturals, for example, 19521450 + ... + 19525171.

It is an arithmetic number, because the mean of its divisors is an integer number (18176202541).

Almost surely, 2^72665761681 is an apocalyptic number.

It is an amenable number.

72665761681 is a deficient number, since it is larger than the sum of its proper divisors (39048483).

72665761681 is a wasteful number, since it uses less digits than its factorization.

72665761681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39048482.

The product of its digits is 5080320, while the sum is 55.

The spelling of 72665761681 in words is "seventy-two billion, six hundred sixty-five million, seven hundred sixty-one thousand, six hundred eighty-one".