661644289 has 4 divisors (see below), whose sum is σ = 690411456. Its totient is φ = 632877124.

The previous prime is 661644287. The next prime is 661644299. The reversal of 661644289 is 982446166.

661644289 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 661644289 - 2¹ = 661644287 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661644287) 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, 14383549 + ... + 14383594.

It is an arithmetic number, because the mean of its divisors is an integer number (172602864).

Almost surely, 2^661644289 is an apocalyptic number.

It is an amenable number.

661644289 is a deficient number, since it is larger than the sum of its proper divisors (28767167).

661644289 is a wasteful number, since it uses less digits than its factorization.

661644289 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28767166.

The product of its digits is 497664, while the sum is 46.

The square root of 661644289 is about 25722.4471814017. The cubic root of 661644289 is about 871.3812071965.

It can be divided in two parts, 6616 and 44289, that added together give a palindrome (50905).

The spelling of 661644289 in words is "six hundred sixty-one million, six hundred forty-four thousand, two hundred eighty-nine".