661638 has 8 divisors (see below), whose sum is σ = 1323288. Its totient is φ = 220544.

The previous prime is 661621. The next prime is 661663. The reversal of 661638 is 836166.

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

661638 is an admirable 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 661638.

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 3 ways as a sum of consecutive naturals, for example, 55131 + ... + 55142.

It is an arithmetic number, because the mean of its divisors is an integer number (165411).

2⁶⁶¹⁶³⁸ is an apocalyptic number.

661638 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

661638 is a wasteful number, since it uses less digits than its factorization.

661638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 110278.

The product of its digits is 5184, while the sum is 30.

The square root of 661638 is about 813.4113350575. The cubic root of 661638 is about 87.1378446330.

The spelling of 661638 in words is "six hundred sixty-one thousand, six hundred thirty-eight".