656981 has 8 divisors (see below), whose sum is σ = 716184. Its totient is φ = 599040.

The previous prime is 656977. The next prime is 656989. The reversal of 656981 is 189656.

It can be written as a sum of positive squares in 4 ways, for example, as 2500 + 654481 = 50^2 + 809^2 .

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

It is not a de Polignac number, because 656981 - 2² = 656977 is a prime.

It is a super-2 number, since 2×656981² = 863248068722, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 656981.

It is not an unprimeable number, because it can be changed into a prime (656989) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1001 + ... + 1521.

It is an arithmetic number, because the mean of its divisors is an integer number (89523).

2⁶⁵⁶⁹⁸¹ is an apocalyptic number.

It is an amenable number.

656981 is a deficient number, since it is larger than the sum of its proper divisors (59203).

656981 is a wasteful number, since it uses less digits than its factorization.

656981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 631.

The product of its digits is 12960, while the sum is 35.

The square root of 656981 is about 810.5436447225. The cubic root of 656981 is about 86.9329205043.

The spelling of 656981 in words is "six hundred fifty-six thousand, nine hundred eighty-one".