421721 has 8 divisors (see below), whose sum is σ = 439560. Its totient is φ = 404352.

The previous prime is 421717. The next prime is 421727. The reversal of 421721 is 127124.

It can be written as a sum of positive squares in 4 ways, for example, as 151321 + 270400 = 389^2 + 520^2 .

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 421721 - 2² = 421717 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 421721.

It is not an unprimeable number, because it can be changed into a prime (421727) 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, 3815 + ... + 3923.

It is an arithmetic number, because the mean of its divisors is an integer number (54945).

2⁴²¹⁷²¹ is an apocalyptic number.

It is an amenable number.

421721 is a deficient number, since it is larger than the sum of its proper divisors (17839).

421721 is a wasteful number, since it uses less digits than its factorization.

421721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 235.

The product of its digits is 112, while the sum is 17.

The square root of 421721 is about 649.4004927624. The cubic root of 421721 is about 74.9908729634.

Adding to 421721 its reverse (127124), we get a palindrome (548845).

The spelling of 421721 in words is "four hundred twenty-one thousand, seven hundred twenty-one", and thus it is an iban number.