661409 has 8 divisors (see below), whose sum is σ = 795840. Its totient is φ = 536976.

The previous prime is 661393. The next prime is 661417. The reversal of 661409 is 904166.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 661409 - 2⁴ = 661393 is a prime.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 661409.

It is not an unprimeable number, because it can be changed into a prime (661439) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2354 + ... + 2619.

It is an arithmetic number, because the mean of its divisors is an integer number (99480).

2⁶⁶¹⁴⁰⁹ is an apocalyptic number.

It is an amenable number.

661409 is a deficient number, since it is larger than the sum of its proper divisors (134431).

661409 is a wasteful number, since it uses less digits than its factorization.

661409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4999.

The product of its (nonzero) digits is 1296, while the sum is 26.

The square root of 661409 is about 813.2705576867. The cubic root of 661409 is about 87.1277903591.

The spelling of 661409 in words is "six hundred sixty-one thousand, four hundred nine".