66887561 has 4 divisors (see below), whose sum is σ = 72032772. Its totient is φ = 61742352.

The previous prime is 66887551. The next prime is 66887563. The reversal of 66887561 is 16578866.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 16578866 = 2 ⋅8289433.

It can be written as a sum of positive squares in 2 ways, for example, as 5359225 + 61528336 = 2315^2 + 7844^2 .

It is a cyclic number.

It is not a de Polignac number, because 66887561 - 2⁶ = 66887497 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (66887563) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2572586 + ... + 2572611.

It is an arithmetic number, because the mean of its divisors is an integer number (18008193).

Almost surely, 2^66887561 is an apocalyptic number.

It is an amenable number.

66887561 is a deficient number, since it is larger than the sum of its proper divisors (5145211).

66887561 is a wasteful number, since it uses less digits than its factorization.

66887561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5145210.

The product of its digits is 483840, while the sum is 47.

The square root of 66887561 is about 8178.4815827878. The cubic root of 66887561 is about 405.9274806370.

The spelling of 66887561 in words is "sixty-six million, eight hundred eighty-seven thousand, five hundred sixty-one".