66709840 has 20 divisors (see below), whose sum is σ = 155100564. Its totient is φ = 26683904.

The previous prime is 66709807. The next prime is 66709847. The reversal of 66709840 is 4890766.

It can be written as a sum of positive squares in 2 ways, for example, as 47279376 + 19430464 = 6876^2 + 4408^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a junction number, because it is equal to n+sod(n) for n = 66709793 and 66709802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66709847) 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, 416857 + ... + 417016.

Almost surely, 2^66709840 is an apocalyptic number.

It is an amenable number.

66709840 is an abundant number, since it is smaller than the sum of its proper divisors (88390724).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

66709840 is a wasteful number, since it uses less digits than its factorization.

66709840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 833886 (or 833880 counting only the distinct ones).

The product of its (nonzero) digits is 72576, while the sum is 40.

The square root of 66709840 is about 8167.6091973110. The cubic root of 66709840 is about 405.5676437950.

The spelling of 66709840 in words is "sixty-six million, seven hundred nine thousand, eight hundred forty".