661655 has 4 divisors (see below), whose sum is σ = 793992. Its totient is φ = 529320.

The previous prime is 661621. The next prime is 661663. The reversal of 661655 is 556166.

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

It is not a de Polignac number, because 661655 - 2¹⁶ = 596119 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 66161 + ... + 66170.

It is an arithmetic number, because the mean of its divisors is an integer number (198498).

2⁶⁶¹⁶⁵⁵ is an apocalyptic number.

661655 is a deficient number, since it is larger than the sum of its proper divisors (132337).

661655 is a wasteful number, since it uses less digits than its factorization.

661655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 132336.

The product of its digits is 5400, while the sum is 29.

The square root of 661655 is about 813.4217848079. The cubic root of 661655 is about 87.1385909277.

The spelling of 661655 in words is "six hundred sixty-one thousand, six hundred fifty-five".