42661 has 4 divisors (see below), whose sum is σ = 43852. Its totient is φ = 41472.

The previous prime is 42649. The next prime is 42667. The reversal of 42661 is 16624.

42661 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 36100 + 6561 = 190^2 + 81^2 .

It is a 5-Lehmer number, since φ(42661) divides (42661-1)⁵.

It is a cyclic number.

It is not a de Polignac number, because 42661 - 2⁷ = 42533 is a prime.

It is a Duffinian number.

42661 is a lucky number.

It is a nialpdrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (42667) 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, 540 + ... + 613.

It is an arithmetic number, because the mean of its divisors is an integer number (10963).

2⁴²⁶⁶¹ is an apocalyptic number.

It is an amenable number.

42661 is a deficient number, since it is larger than the sum of its proper divisors (1191).

42661 is a wasteful number, since it uses less digits than its factorization.

42661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1190.

The product of its digits is 288, while the sum is 19.

The square root of 42661 is about 206.5453945262. The cubic root of 42661 is about 34.9416715556.

It can be divided in two parts, 42 and 661, that added together give a triangular number (703 = T₃₇).

The spelling of 42661 in words is "forty-two thousand, six hundred sixty-one".