66639873609 has 27 divisors (see below), whose sum is σ = 99986105037. Its totient is φ = 44412642468.

The previous prime is 66639873551. The next prime is 66639873617. The reversal of 66639873609 is 90637893666.

The square root of 66639873609 is 258147.

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

It is a tau number, because it is divible by the number of its divisors (27).

It is not a de Polignac number, because 66639873609 - 2¹³ = 66639865417 is a prime.

It is not an unprimeable number, because it can be changed into a prime (66639872609) 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, 20908314 + ... + 20911500.

Almost surely, 2^66639873609 is an apocalyptic number.

66639873609 is the 258147-th square number.

66639873609 is the 129074-th centered octagonal number.

It is an amenable number.

66639873609 is a deficient number, since it is larger than the sum of its proper divisors (33346231428).

66639873609 is an frugal number, since it uses more digits than its factorization.

66639873609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6398 (or 3190 counting only the distinct ones).

The product of its (nonzero) digits is 52907904, while the sum is 63.

The spelling of 66639873609 in words is "sixty-six billion, six hundred thirty-nine million, eight hundred seventy-three thousand, six hundred nine".