635681 has 8 divisors (see below), whose sum is σ = 685224. Its totient is φ = 587520.

The previous prime is 635659. The next prime is 635689. The reversal of 635681 is 186536.

It can be written as a sum of positive squares in 4 ways, for example, as 10000 + 625681 = 100^2 + 791^2 .

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

It is not a de Polignac number, because 635681 - 2⁶ = 635617 is a prime.

It is a super-2 number, since 2×635681² = 808180667522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (635689) 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, 731 + ... + 1343.

It is an arithmetic number, because the mean of its divisors is an integer number (85653).

2⁶³⁵⁶⁸¹ is an apocalyptic number.

635681 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

It is an amenable number.

635681 is a deficient number, since it is larger than the sum of its proper divisors (49543).

635681 is a wasteful number, since it uses less digits than its factorization.

635681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 691.

The product of its digits is 4320, while the sum is 29.

The square root of 635681 is about 797.2960554273. The cubic root of 635681 is about 85.9830956499.

The spelling of 635681 in words is "six hundred thirty-five thousand, six hundred eighty-one".