661406 has 4 divisors (see below), whose sum is σ = 992112. Its totient is φ = 330702.

The previous prime is 661393. The next prime is 661417. The reversal of 661406 is 604166.

It is a semiprime because it is the product of two primes.

It is a Curzon number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 661406.

It is an unprimeable number.

661406 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 165350 + ... + 165353.

It is an arithmetic number, because the mean of its divisors is an integer number (248028).

2⁶⁶¹⁴⁰⁶ is an apocalyptic number.

661406 is a deficient number, since it is larger than the sum of its proper divisors (330706).

661406 is a wasteful number, since it uses less digits than its factorization.

661406 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 330705.

The product of its (nonzero) digits is 864, while the sum is 23.

The square root of 661406 is about 813.2687132799. The cubic root of 661406 is about 87.1276586284.

The spelling of 661406 in words is "six hundred sixty-one thousand, four hundred six".