661329 has 12 divisors (see below), whose sum is σ = 962676. Its totient is φ = 437472.

The previous prime is 661327. The next prime is 661343. The reversal of 661329 is 923166.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 540225 + 121104 = 735^2 + 348^2 .

It is not a de Polignac number, because 661329 - 2¹ = 661327 is a prime.

It is not an unprimeable number, because it can be changed into a prime (661321) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1587 + ... + 1959.

It is an arithmetic number, because the mean of its divisors is an integer number (80223).

2⁶⁶¹³²⁹ is an apocalyptic number.

It is an amenable number.

661329 is a deficient number, since it is larger than the sum of its proper divisors (301347).

661329 is a wasteful number, since it uses less digits than its factorization.

661329 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 576 (or 573 counting only the distinct ones).

The product of its digits is 1944, while the sum is 27.

The square root of 661329 is about 813.2213720753. The cubic root of 661329 is about 87.1242774021.

It can be divided in two parts, 661 and 329, that added together give a triangular number (990 = T₄₄).

The spelling of 661329 in words is "six hundred sixty-one thousand, three hundred twenty-nine".