61665821172 has 18 divisors (see below), whose sum is σ = 155877492498. Its totient is φ = 20555273712.

The previous prime is 61665821159. The next prime is 61665821177. The reversal of 61665821172 is 27112856616.

61665821172 is a `hidden beast` number, since 6 + 1 + 66 + 582 + 1 + 1 + 7 + 2 = 666.

It can be written as a sum of positive squares in only one way, i.e., 31554548496 + 30111272676 = 177636^2 + 173526^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a super-3 number, since 3×61665821172³ (a number of 33 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (61665821177) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 856469703 + ... + 856469774.

Almost surely, 2^61665821172 is an apocalyptic number.

It is an amenable number.

61665821172 is an abundant number, since it is smaller than the sum of its proper divisors (94211671326).

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

61665821172 is a wasteful number, since it uses less digits than its factorization.

61665821172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1712939487 (or 1712939482 counting only the distinct ones).

The product of its digits is 241920, while the sum is 45.

The spelling of 61665821172 in words is "sixty-one billion, six hundred sixty-five million, eight hundred twenty-one thousand, one hundred seventy-two".