66311915121 has 9 divisors (see below), whose sum is σ = 95784993291. Its totient is φ = 44207428392.

The previous prime is 66311915107. The next prime is 66311915141. The reversal of 66311915121 is 12151911366.

The square root of 66311915121 is 257511.

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

66311915121 is a `hidden beast` number, since 6 + 631 + 1 + 9 + 1 + 5 + 12 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 62787830625 + 3524084496 = 250575^2 + 59364^2 .

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 66311915121 - 2³¹ = 64164431473 is a prime.

It is not an unprimeable number, because it can be changed into a prime (66311915101) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 729615 + ... + 815451.

Almost surely, 2^66311915121 is an apocalyptic number.

66311915121 is the 257511-st square number.

66311915121 is the 128756-th centered octagonal number.

It is an amenable number.

66311915121 is a deficient number, since it is larger than the sum of its proper divisors (29473078170).

66311915121 is an frugal number, since it uses more digits than its factorization.

66311915121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 171680 (or 85840 counting only the distinct ones).

The product of its digits is 9720, while the sum is 36.

Multiplying 66311915121 by its sum of digits (36), we get a square (2387228944356 = 1545066²).

The spelling of 66311915121 in words is "sixty-six billion, three hundred eleven million, nine hundred fifteen thousand, one hundred twenty-one".