521621 has 4 divisors (see below), whose sum is σ = 524544. Its totient is φ = 518700.

The previous prime is 521603. The next prime is 521641. The reversal of 521621 is 126125.

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 521621 - 2⁶ = 521557 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 521621.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 521621.

It is not an unprimeable number, because it can be changed into a prime (521641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1175 + ... + 1556.

It is an arithmetic number, because the mean of its divisors is an integer number (131136).

2⁵²¹⁶²¹ is an apocalyptic number.

It is an amenable number.

521621 is a deficient number, since it is larger than the sum of its proper divisors (2923).

521621 is a wasteful number, since it uses less digits than its factorization.

521621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2922.

The product of its digits is 120, while the sum is 17.

The square root of 521621 is about 722.2333417947. The cubic root of 521621 is about 80.4979874244.

Adding to 521621 its reverse (126125), we get a palindrome (647746).

The spelling of 521621 in words is "five hundred twenty-one thousand, six hundred twenty-one".