66439025640 has 384 divisors, whose sum is σ = 239649490080. Its totient is φ = 15858892800.

The previous prime is 66439025623. The next prime is 66439025657. The reversal of 66439025640 is 4652093466.

66439025640 is a `hidden beast` number, since 6 + 6 + 4 + 390 + 256 + 4 + 0 = 666.

66439025640 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (66439025623) and next prime (66439025657).

It can be written as a sum of positive squares in 16 ways, for example, as 5322286116 + 61116739524 = 72954^2 + 247218^2 .

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 34729324 + ... + 34731236.

Almost surely, 2^66439025640 is an apocalyptic number.

66439025640 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 66439025640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (119824745040).

66439025640 is an abundant number, since it is smaller than the sum of its proper divisors (173210464440).

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

66439025640 is a wasteful number, since it uses less digits than its factorization.

66439025640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2165 (or 2158 counting only the distinct ones).

The product of its (nonzero) digits is 933120, while the sum is 45.

The spelling of 66439025640 in words is "sixty-six billion, four hundred thirty-nine million, twenty-five thousand, six hundred forty".