661635 has 48 divisors (see below), whose sum is σ = 1317600. Its totient is φ = 314496.

The previous prime is 661621. The next prime is 661663. The reversal of 661635 is 536166.

It is not a de Polignac number, because 661635 - 2⁵ = 661603 is a prime.

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

661635 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 661599 and 661608.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 22801 + ... + 22829.

It is an arithmetic number, because the mean of its divisors is an integer number (27450).

2⁶⁶¹⁶³⁵ is an apocalyptic number.

661635 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

661635 is a deficient number, since it is larger than the sum of its proper divisors (655965).

661635 is a wasteful number, since it uses less digits than its factorization.

661635 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 69 (or 50 counting only the distinct ones).

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

The square root of 661635 is about 813.4094909700. The cubic root of 661635 is about 87.1377129327.

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

The spelling of 661635 in words is "six hundred sixty-one thousand, six hundred thirty-five".