66532561661 has 4 divisors (see below), whose sum is σ = 66634449852. Its totient is φ = 66430673472.

The previous prime is 66532561651. The next prime is 66532561673. The reversal of 66532561661 is 16616523566.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 16616523566 = 2 ⋅8308261783.

It can be written as a sum of positive squares in 2 ways, for example, as 6529609636 + 60002952025 = 80806^2 + 244955^2 .

It is a cyclic number.

It is not a de Polignac number, because 66532561661 - 2¹⁸ = 66532299517 is a prime.

It is a super-2 number, since 2×66532561661² (a number of 22 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66532561621) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 50943116 + ... + 50944421.

It is an arithmetic number, because the mean of its divisors is an integer number (16658612463).

Almost surely, 2^66532561661 is an apocalyptic number.

It is an amenable number.

66532561661 is a deficient number, since it is larger than the sum of its proper divisors (101888191).

66532561661 is a wasteful number, since it uses less digits than its factorization.

66532561661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 101888190.

The product of its digits is 1166400, while the sum is 47.

The spelling of 66532561661 in words is "sixty-six billion, five hundred thirty-two million, five hundred sixty-one thousand, six hundred sixty-one".