66401856 has 70 divisors (see below), whose sum is σ = 196851270. Its totient is φ = 22132224.

The previous prime is 66401767. The next prime is 66401857. The reversal of 66401856 is 65810466.

66401856 is a `hidden beast` number, since 6 + 640 + 1 + 8 + 5 + 6 = 666.

66401856 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 51840000 + 14561856 = 7200^2 + 3816^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 66401856.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66401857) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 1221 + ... + 11588.

It is an arithmetic number, because the mean of its divisors is an integer number (2812161).

Almost surely, 2^66401856 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 66401856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (98425635).

66401856 is an abundant number, since it is smaller than the sum of its proper divisors (130449414).

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

66401856 is a wasteful number, since it uses less digits than its factorization.

66401856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12833 (or 12814 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 36.

The square root of 66401856 is about 8148.7333985105. The cubic root of 66401856 is about 404.9425432894.

The spelling of 66401856 in words is "sixty-six million, four hundred one thousand, eight hundred fifty-six".