661871 has 8 divisors (see below), whose sum is σ = 789504. Its totient is φ = 542520.

The previous prime is 661849. The next prime is 661873. The reversal of 661871 is 178166.

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

It is a cyclic number.

It is not a de Polignac number, because 661871 - 2¹⁸ = 399727 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661873) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1895 + ... + 2216.

It is an arithmetic number, because the mean of its divisors is an integer number (98688).

2⁶⁶¹⁸⁷¹ is an apocalyptic number.

661871 is a deficient number, since it is larger than the sum of its proper divisors (127633).

661871 is a wasteful number, since it uses less digits than its factorization.

661871 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4141.

The product of its digits is 2016, while the sum is 29.

The square root of 661871 is about 813.5545464196. The cubic root of 661871 is about 87.1480721467.

The spelling of 661871 in words is "six hundred sixty-one thousand, eight hundred seventy-one".