65540608081 has 27 divisors (see below), whose sum is σ = 72685608411. Its totient is φ = 59070492624.

The previous prime is 65540608073. The next prime is 65540608109. The reversal of 65540608081 is 18080604556.

The square root of 65540608081 is 256009.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 9695356225 + 55845251856 = 98465^2 + 236316^2 .

It is not a de Polignac number, because 65540608081 - 2³ = 65540608073 is a prime.

It is a super-2 number, since 2×65540608081² (a number of 22 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (65540608031) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 156421290 + ... + 156421708.

Almost surely, 2^65540608081 is an apocalyptic number.

65540608081 is the 256009-th square number.

65540608081 is the 128005-th centered octagonal number.

It is an amenable number.

65540608081 is a deficient number, since it is larger than the sum of its proper divisors (7145000330).

65540608081 is an frugal number, since it uses more digits than its factorization.

65540608081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 958 (or 479 counting only the distinct ones).

The product of its (nonzero) digits is 230400, while the sum is 43.

The spelling of 65540608081 in words is "sixty-five billion, five hundred forty million, six hundred eight thousand, eighty-one".