660643261 has 4 divisors (see below), whose sum is σ = 660723712. Its totient is φ = 660562812.

The previous prime is 660643253. The next prime is 660643279. The reversal of 660643261 is 162346066.

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 660643261 - 2³ = 660643253 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (660643241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26301 + ... + 44866.

It is an arithmetic number, because the mean of its divisors is an integer number (165180928).

Almost surely, 2^660643261 is an apocalyptic number.

It is an amenable number.

660643261 is a deficient number, since it is larger than the sum of its proper divisors (80451).

660643261 is an equidigital number, since it uses as much as digits as its factorization.

660643261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80450.

The product of its (nonzero) digits is 31104, while the sum is 34.

The square root of 660643261 is about 25702.9815585663. The cubic root of 660643261 is about 870.9415362773.

The spelling of 660643261 in words is "six hundred sixty million, six hundred forty-three thousand, two hundred sixty-one".