66156636321261 has 24 divisors (see below), whose sum is σ = 95811051027224. Its totient is φ = 43988388301440.

The previous prime is 66156636321253. The next prime is 66156636321317. The reversal of 66156636321261 is 16212363665166.

66156636321261 is a `hidden beast` number, since 6 + 6 + 1 + 5 + 6 + 6 + 363 + 212 + 61 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 2099583612036 + 64057052709225 = 1448994^2 + 8003565^2 .

It is not a de Polignac number, because 66156636321261 - 2³ = 66156636321253 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 66156636321198 and 66156636321207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66156636322261) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 30910755 + ... + 32981631.

Almost surely, 2^{66156636321261} is an apocalyptic number.

It is an amenable number.

66156636321261 is a deficient number, since it is larger than the sum of its proper divisors (29654414705963).

66156636321261 is a wasteful number, since it uses less digits than its factorization.

66156636321261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2080221 (or 2080218 counting only the distinct ones).

The product of its digits is 8398080, while the sum is 54.

The spelling of 66156636321261 in words is "sixty-six trillion, one hundred fifty-six billion, six hundred thirty-six million, three hundred twenty-one thousand, two hundred sixty-one".