635881 has 4 divisors (see below), whose sum is σ = 663552. Its totient is φ = 608212.

The previous prime is 635879. The next prime is 635891. The reversal of 635881 is 188536.

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 635881 - 2¹ = 635879 is a prime.

It is a super-2 number, since 2×635881² = 808689292322, which contains 22 as substring.

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 nialpdrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (635801) 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, 13801 + ... + 13846.

It is an arithmetic number, because the mean of its divisors is an integer number (165888).

2⁶³⁵⁸⁸¹ is an apocalyptic number.

It is an amenable number.

635881 is a deficient number, since it is larger than the sum of its proper divisors (27671).

635881 is a wasteful number, since it uses less digits than its factorization.

635881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27670.

The product of its digits is 5760, while the sum is 31.

The square root of 635881 is about 797.4214694877. The cubic root of 635881 is about 85.9921121303.

The spelling of 635881 in words is "six hundred thirty-five thousand, eight hundred eighty-one".