66865561 has 8 divisors (see below), whose sum is σ = 79053120. Its totient is φ = 55336848.

The previous prime is 66865553. The next prime is 66865583. The reversal of 66865561 is 16556866.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 66865561 - 2³ = 66865553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66865511) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 164491 + ... + 164896.

It is an arithmetic number, because the mean of its divisors is an integer number (9881640).

Almost surely, 2^66865561 is an apocalyptic number.

It is an amenable number.

66865561 is a deficient number, since it is larger than the sum of its proper divisors (12187559).

66865561 is a wasteful number, since it uses less digits than its factorization.

66865561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 329423.

The product of its digits is 259200, while the sum is 43.

The square root of 66865561 is about 8177.1364792328. The cubic root of 66865561 is about 405.8829711960.

The spelling of 66865561 in words is "sixty-six million, eight hundred sixty-five thousand, five hundred sixty-one".