66439840 has 48 divisors (see below), whose sum is σ = 158887008. Its totient is φ = 26250496.

The previous prime is 66439823. The next prime is 66439843. The reversal of 66439840 is 4893466.

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 = 66439793 and 66439802.

It is not an unprimeable number, because it can be changed into a prime (66439843) 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, 10779 + ... + 15781.

It is an arithmetic number, because the mean of its divisors is an integer number (3310146).

Almost surely, 2^66439840 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 66439840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (79443504).

66439840 is an abundant number, since it is smaller than the sum of its proper divisors (92447168).

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

66439840 is a wasteful number, since it uses less digits than its factorization.

66439840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5101 (or 5093 counting only the distinct ones).

The product of its (nonzero) digits is 124416, while the sum is 40.

The square root of 66439840 is about 8151.0637342619. The cubic root of 66439840 is about 405.0197419630.

It can be divided in two parts, 664 and 39840, that added together give a palindrome (40504).

The spelling of 66439840 in words is "sixty-six million, four hundred thirty-nine thousand, eight hundred forty".