660981 has 4 divisors (see below), whose sum is σ = 881312. Its totient is φ = 440652.

The previous prime is 660973. The next prime is 660983. The reversal of 660981 is 189066.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 660981 - 2³ = 660973 is a prime.

It is a super-2 number, since 2×660981² = 873791764722, which contains 22 as substring.

It is a D-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 (660983) 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 3 ways as a sum of consecutive naturals, for example, 110161 + ... + 110166.

It is an arithmetic number, because the mean of its divisors is an integer number (220328).

2⁶⁶⁰⁹⁸¹ is an apocalyptic number.

It is an amenable number.

660981 is a deficient number, since it is larger than the sum of its proper divisors (220331).

660981 is a wasteful number, since it uses less digits than its factorization.

660981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 220330.

The product of its (nonzero) digits is 2592, while the sum is 30.

The square root of 660981 is about 813.0073800403. The cubic root of 660981 is about 87.1089927413.

The spelling of 660981 in words is "six hundred sixty thousand, nine hundred eighty-one".