66401559225 has 81 divisors (see below), whose sum is σ = 122195750989. Its totient is φ = 34467945600.

The previous prime is 66401559181. The next prime is 66401559247. The reversal of 66401559225 is 52295510466.

The square root of 66401559225 is 257685.

It is a perfect power (a square), and thus also a powerful number.

66401559225 is a `hidden beast` number, since 6 + 6 + 40 + 15 + 592 + 2 + 5 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 27949486761 + 38452072464 = 167181^2 + 196092^2 .

It is not a de Polignac number, because 66401559225 - 2¹¹ = 66401557177 is a prime.

It is a super-2 number, since 2×66401559225² (a number of 22 digits) contains 22 as substring.

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

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 158476066 + ... + 158476484.

Almost surely, 2^66401559225 is an apocalyptic number.

66401559225 is the 257685-th square number.

66401559225 is the 128843-rd centered octagonal number.

It is an amenable number.

66401559225 is a deficient number, since it is larger than the sum of its proper divisors (55794191764).

66401559225 is an equidigital number, since it uses as much as digits as its factorization.

66401559225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 936 (or 468 counting only the distinct ones).

The product of its (nonzero) digits is 648000, while the sum is 45.

The spelling of 66401559225 in words is "sixty-six billion, four hundred one million, five hundred fifty-nine thousand, two hundred twenty-five".