661693 has 4 divisors (see below), whose sum is σ = 684540. Its totient is φ = 638848.

The previous prime is 661679. The next prime is 661697. The reversal of 661693 is 396166.

661693 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 396166 = 2 ⋅198083.

It can be written as a sum of positive squares in 2 ways, for example, as 558009 + 103684 = 747^2 + 322^2 .

It is a cyclic number.

It is not a de Polignac number, because 661693 - 2¹³ = 653501 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax 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 (661697) 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, 11380 + ... + 11437.

It is an arithmetic number, because the mean of its divisors is an integer number (171135).

2⁶⁶¹⁶⁹³ is an apocalyptic number.

It is an amenable number.

661693 is a deficient number, since it is larger than the sum of its proper divisors (22847).

661693 is a wasteful number, since it uses less digits than its factorization.

661693 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22846.

The product of its digits is 5832, while the sum is 31.

The square root of 661693 is about 813.4451425880. The cubic root of 661693 is about 87.1402590695.

The spelling of 661693 in words is "six hundred sixty-one thousand, six hundred ninety-three".