660421 has 4 divisors (see below), whose sum is σ = 695200. Its totient is φ = 625644.

The previous prime is 660409. The next prime is 660449. The reversal of 660421 is 124066.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 660421 - 2¹³ = 652229 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (19), and also a Moran number because the ratio is a prime number: 34759 = 660421 / (6 + 6 + 0 + 4 + 2 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (660521) 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, 17361 + ... + 17398.

It is an arithmetic number, because the mean of its divisors is an integer number (173800).

2⁶⁶⁰⁴²¹ is an apocalyptic number.

It is an amenable number.

660421 is a deficient number, since it is larger than the sum of its proper divisors (34779).

660421 is a wasteful number, since it uses less digits than its factorization.

660421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34778.

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

The square root of 660421 is about 812.6629067455. The cubic root of 660421 is about 87.0843854689.

Adding to 660421 its reverse (124066), we get a palindrome (784487).

It can be divided in two parts, 660 and 421, that added together give a triangular number (1081 = T₄₆).

The spelling of 660421 in words is "six hundred sixty thousand, four hundred twenty-one".