661218841 has 4 divisors (see below), whose sum is σ = 672426000. Its totient is φ = 650011684.

The previous prime is 661218799. The next prime is 661218847. The reversal of 661218841 is 148812166.

661218841 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 661218841 - 2¹¹ = 661216793 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 661218841.

It is not an unprimeable number, because it can be changed into a prime (661218847) 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, 5603491 + ... + 5603608.

It is an arithmetic number, because the mean of its divisors is an integer number (168106500).

Almost surely, 2^661218841 is an apocalyptic number.

It is an amenable number.

661218841 is a deficient number, since it is larger than the sum of its proper divisors (11207159).

661218841 is a wasteful number, since it uses less digits than its factorization.

661218841 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11207158.

The product of its digits is 18432, while the sum is 37.

The square root of 661218841 is about 25714.1758763527. The cubic root of 661218841 is about 871.1943964042.

The spelling of 661218841 in words is "six hundred sixty-one million, two hundred eighteen thousand, eight hundred forty-one".