635661 has 16 divisors (see below), whose sum is σ = 1014720. Its totient is φ = 390960.

The previous prime is 635659. The next prime is 635689. The reversal of 635661 is 166536.

635661 = T₂₀₈ + T₂₀₉ + ... + T₂₃₃.

635661 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 635661 - 2¹ = 635659 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

635661 is a lucky 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 635661.

It is not an unprimeable number, because it can be changed into a prime (635461) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 555 + ... + 1256.

It is an arithmetic number, because the mean of its divisors is an integer number (63420).

2⁶³⁵⁶⁶¹ is an apocalyptic number.

It is an amenable number.

635661 is a deficient number, since it is larger than the sum of its proper divisors (379059).

635661 is a wasteful number, since it uses less digits than its factorization.

635661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1833 (or 1827 counting only the distinct ones).

The product of its digits is 3240, while the sum is 27.

The square root of 635661 is about 797.2835129363. The cubic root of 635661 is about 85.9821938978.

It can be divided in two parts, 635 and 661, that added together give a 4-th power (1296 = 6⁴).

The spelling of 635661 in words is "six hundred thirty-five thousand, six hundred sixty-one".