661783 has 4 divisors (see below), whose sum is σ = 670240. Its totient is φ = 653328.

The previous prime is 661777. The next prime is 661823. The reversal of 661783 is 387166.

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

It is a cyclic number.

It is not a de Polignac number, because 661783 - 2¹⁷ = 530711 is a prime.

It is the 814-th Hogben number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661183) by changing a digit.

It is a nontrivial repunit in base 813.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4110 + ... + 4267.

It is an arithmetic number, because the mean of its divisors is an integer number (167560).

2⁶⁶¹⁷⁸³ is an apocalyptic number.

661783 is a deficient number, since it is larger than the sum of its proper divisors (8457).

661783 is an equidigital number, since it uses as much as digits as its factorization.

661783 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8456.

The product of its digits is 6048, while the sum is 31.

The square root of 661783 is about 813.5004609710. The cubic root of 661783 is about 87.1442096769.

It can be divided in two parts, 661 and 783, that added together give a square (1444 = 38²).

The spelling of 661783 in words is "six hundred sixty-one thousand, seven hundred eighty-three".