66561550016601 has 4 divisors (see below), whose sum is σ = 88748733355472. Its totient is φ = 44374366677732.

The previous prime is 66561550016567. The next prime is 66561550016609. The reversal of 66561550016601 is 10661005516566.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 66561550016601 - 2¹⁴ = 66561550000217 is a prime.

It is a super-2 number, since 2×66561550016601² (a number of 28 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66561550016609) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11093591669431 + ... + 11093591669436.

It is an arithmetic number, because the mean of its divisors is an integer number (22187183338868).

Almost surely, 2^{66561550016601} is an apocalyptic number.

It is an amenable number.

66561550016601 is a deficient number, since it is larger than the sum of its proper divisors (22187183338871).

66561550016601 is a wasteful number, since it uses less digits than its factorization.

66561550016601 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22187183338870.

The product of its (nonzero) digits is 972000, while the sum is 48.

The spelling of 66561550016601 in words is "sixty-six trillion, five hundred sixty-one billion, five hundred fifty million, sixteen thousand, six hundred one".