621921 has 4 divisors (see below), whose sum is σ = 829232. Its totient is φ = 414612.

The previous prime is 621913. The next prime is 621923. The reversal of 621921 is 129126.

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 not a de Polignac number, because 621921 - 2³ = 621913 is a prime.

It is a D-number.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (621923) 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 3 ways as a sum of consecutive naturals, for example, 103651 + ... + 103656.

It is an arithmetic number, because the mean of its divisors is an integer number (207308).

2⁶²¹⁹²¹ is an apocalyptic number.

It is an amenable number.

621921 is a deficient number, since it is larger than the sum of its proper divisors (207311).

621921 is a wasteful number, since it uses less digits than its factorization.

621921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 207310.

The product of its digits is 216, while the sum is 21.

The square root of 621921 is about 788.6196802008. The cubic root of 621921 is about 85.3581657195.

The spelling of 621921 in words is "six hundred twenty-one thousand, nine hundred twenty-one".