64661220161 has 4 divisors (see below), whose sum is σ = 64662346800. Its totient is φ = 64660093524.

The previous prime is 64661220121. The next prime is 64661220187. The reversal of 64661220161 is 16102216646.

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 a cyclic number.

It is not a de Polignac number, because 64661220161 - 2²² = 64657025857 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (64661220121) 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, 472331 + ... + 593648.

It is an arithmetic number, because the mean of its divisors is an integer number (16165586700).

Almost surely, 2^64661220161 is an apocalyptic number.

It is an amenable number.

64661220161 is a deficient number, since it is larger than the sum of its proper divisors (1126639).

64661220161 is a wasteful number, since it uses less digits than its factorization.

64661220161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1126638.

The product of its (nonzero) digits is 20736, while the sum is 35.

The spelling of 64661220161 in words is "sixty-four billion, six hundred sixty-one million, two hundred twenty thousand, one hundred sixty-one".