686421 has 8 divisors (see below), whose sum is σ = 1016960. Its totient is φ = 457596.

The previous prime is 686417. The next prime is 686423. The reversal of 686421 is 124686.

It is not a de Polignac number, because 686421 - 2² = 686417 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 25423 = 686421 / (6 + 8 + 6 + 4 + 2 + 1).

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (686423) 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, 12685 + ... + 12738.

It is an arithmetic number, because the mean of its divisors is an integer number (127120).

2⁶⁸⁶⁴²¹ is an apocalyptic number.

It is an amenable number.

686421 is a deficient number, since it is larger than the sum of its proper divisors (330539).

686421 is a wasteful number, since it uses less digits than its factorization.

686421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25432 (or 25426 counting only the distinct ones).

The product of its digits is 2304, while the sum is 27.

The square root of 686421 is about 828.5052806108. The cubic root of 686421 is about 88.2125115297.

The spelling of 686421 in words is "six hundred eighty-six thousand, four hundred twenty-one".