621020209 has 2 divisors, whose sum is σ = 621020210. Its totient is φ = 621020208.

The previous prime is 621020207. The next prime is 621020243. The reversal of 621020209 is 902020126.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 428365809 + 192654400 = 20697^2 + 13880^2 .

It is a cyclic number.

It is not a de Polignac number, because 621020209 - 2¹ = 621020207 is a prime.

It is a super-3 number, since 3×621020209³ (a number of 27 digits) contains 333 as substring.

Together with 621020207, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 621020209.

It is not a weakly prime, because it can be changed into another prime (621020201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 310510104 + 310510105.

It is an arithmetic number, because the mean of its divisors is an integer number (310510105).

Almost surely, 2^621020209 is an apocalyptic number.

It is an amenable number.

621020209 is a deficient number, since it is larger than the sum of its proper divisors (1).

621020209 is an equidigital number, since it uses as much as digits as its factorization.

621020209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 432, while the sum is 22.

The square root of 621020209 is about 24920.2770650729. The cubic root of 621020209 is about 853.1693485584.

The spelling of 621020209 in words is "six hundred twenty-one million, twenty thousand, two hundred nine".