661655161 has 4 divisors (see below), whose sum is σ = 662471824. Its totient is φ = 660838500.

The previous prime is 661655153. The next prime is 661655173. The reversal of 661655161 is 161556166.

661655161 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 661655161 - 2³ = 661655153 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 661655161.

It is not an unprimeable number, because it can be changed into a prime (661655101) 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, 407115 + ... + 408736.

It is an arithmetic number, because the mean of its divisors is an integer number (165617956).

Almost surely, 2^661655161 is an apocalyptic number.

It is an amenable number.

661655161 is a deficient number, since it is larger than the sum of its proper divisors (816663).

661655161 is an equidigital number, since it uses as much as digits as its factorization.

661655161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 816662.

The product of its digits is 32400, while the sum is 37.

The square root of 661655161 is about 25722.6585134585. The cubic root of 661655161 is about 871.3859799547.

The spelling of 661655161 in words is "six hundred sixty-one million, six hundred fifty-five thousand, one hundred sixty-one".