661687 has 8 divisors (see below), whose sum is σ = 743904. Its totient is φ = 583968.

The previous prime is 661679. The next prime is 661697. The reversal of 661687 is 786166.

661687 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 661687 - 2³ = 661679 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661607) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 808 + ... + 1405.

It is an arithmetic number, because the mean of its divisors is an integer number (92988).

2⁶⁶¹⁶⁸⁷ is an apocalyptic number.

661687 is a deficient number, since it is larger than the sum of its proper divisors (82217).

661687 is a wasteful number, since it uses less digits than its factorization.

661687 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2249.

The product of its digits is 12096, while the sum is 34.

The square root of 661687 is about 813.4414545620. The cubic root of 661687 is about 87.1399956829.

The spelling of 661687 in words is "six hundred sixty-one thousand, six hundred eighty-seven".