661997 has 8 divisors (see below), whose sum is σ = 801216. Its totient is φ = 533952.

The previous prime is 661993. The next prime is 662003. The reversal of 661997 is 799166.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 661997 - 2² = 661993 is a prime.

It is a Duffinian number.

It is a plaindrome in base 14.

It is a self number, because there is not a number n which added to its sum of digits gives 661997.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661993) by changing a digit.

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 in 7 ways as a sum of consecutive naturals, for example, 2663 + ... + 2900.

It is an arithmetic number, because the mean of its divisors is an integer number (100152).

2⁶⁶¹⁹⁹⁷ is an apocalyptic number.

It is an amenable number.

661997 is a deficient number, since it is larger than the sum of its proper divisors (139219).

661997 is a wasteful number, since it uses less digits than its factorization.

661997 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5587.

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

The square root of 661997 is about 813.6319806891. The cubic root of 661997 is about 87.1536019052.

The spelling of 661997 in words is "six hundred sixty-one thousand, nine hundred ninety-seven".