66780379561 has 81 divisors (see below), whose sum is σ = 86197965399. Its totient is φ = 51576297696.

The previous prime is 66780379541. The next prime is 66780379607. The reversal of 66780379561 is 16597308766.

It is a happy number.

The square root of 66780379561 is 258419.

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

It can be written as a sum of positive squares in only one way, i.e., 35018011161 + 31762368400 = 187131^2 + 178220^2 .

It is not a de Polignac number, because 66780379561 - 2¹³ = 66780371369 is a prime.

It is a super-2 number, since 2×66780379561² (a number of 22 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 66780379496 and 66780379505.

It is not an unprimeable number, because it can be changed into a prime (66780379511) by changing a digit.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 996722050 + ... + 996722116.

Almost surely, 2^66780379561 is an apocalyptic number.

66780379561 is the 258419-th square number.

66780379561 is the 129210-th centered octagonal number.

It is an amenable number.

66780379561 is a deficient number, since it is larger than the sum of its proper divisors (19417585838).

66780379561 is an equidigital number, since it uses as much as digits as its factorization.

66780379561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 244 (or 122 counting only the distinct ones).

The product of its (nonzero) digits is 11430720, while the sum is 58.

The spelling of 66780379561 in words is "sixty-six billion, seven hundred eighty million, three hundred seventy-nine thousand, five hundred sixty-one".