66539640 has 96 divisors (see below), whose sum is σ = 206623440. Its totient is φ = 17141760.

The previous prime is 66539633. The next prime is 66539677. The reversal of 66539640 is 4693566.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 115032 + ... + 115608.

Almost surely, 2^66539640 is an apocalyptic number.

66539640 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 66539640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (103311720).

66539640 is an abundant number, since it is smaller than the sum of its proper divisors (140083800).

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

66539640 is a wasteful number, since it uses less digits than its factorization.

66539640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 653 (or 618 counting only the distinct ones).

The product of its (nonzero) digits is 116640, while the sum is 39.

The square root of 66539640 is about 8157.1833374027. The cubic root of 66539640 is about 405.2224353480. Note that the first 3 decimals are identical.

The spelling of 66539640 in words is "sixty-six million, five hundred thirty-nine thousand, six hundred forty".