661799 has 4 divisors (see below), whose sum is σ = 663864. Its totient is φ = 659736.

The previous prime is 661777. The next prime is 661823. The reversal of 661799 is 997166.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 997166 = 2 ⋅498583.

It is a cyclic number.

It is not a de Polignac number, because 661799 - 2¹² = 657703 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661769) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 437 + ... + 1230.

It is an arithmetic number, because the mean of its divisors is an integer number (165966).

2⁶⁶¹⁷⁹⁹ is an apocalyptic number.

661799 is a deficient number, since it is larger than the sum of its proper divisors (2065).

661799 is a wasteful number, since it uses less digits than its factorization.

661799 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2064.

The product of its digits is 20412, while the sum is 38.

The square root of 661799 is about 813.5102949564. The cubic root of 661799 is about 87.1449119696.

The spelling of 661799 in words is "six hundred sixty-one thousand, seven hundred ninety-nine".