65661602891 has 4 divisors (see below), whose sum is σ = 66399373800. Its totient is φ = 64923831984.

The previous prime is 65661602873. The next prime is 65661602933. The reversal of 65661602891 is 19820616656.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 65661602891 - 2¹⁰ = 65661601867 is a prime.

It is a super-2 number, since 2×65661602891² (a number of 22 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (65661602821) 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 3 ways as a sum of consecutive naturals, for example, 368885321 + ... + 368885498.

It is an arithmetic number, because the mean of its divisors is an integer number (16599843450).

Almost surely, 2^65661602891 is an apocalyptic number.

65661602891 is a deficient number, since it is larger than the sum of its proper divisors (737770909).

65661602891 is an equidigital number, since it uses as much as digits as its factorization.

65661602891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 737770908.

The product of its (nonzero) digits is 933120, while the sum is 50.

The spelling of 65661602891 in words is "sixty-five billion, six hundred sixty-one million, six hundred two thousand, eight hundred ninety-one".