621665549 has 2 divisors, whose sum is σ = 621665550. Its totient is φ = 621665548.

The previous prime is 621665507. The next prime is 621665587. The reversal of 621665549 is 945566126.

621665549 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 461820100 + 159845449 = 21490^2 + 12643^2 .

It is a cyclic number.

It is not a de Polignac number, because 621665549 - 2¹⁶ = 621600013 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (621668549) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 310832774 + 310832775.

It is an arithmetic number, because the mean of its divisors is an integer number (310832775).

Almost surely, 2^621665549 is an apocalyptic number.

It is an amenable number.

621665549 is a deficient number, since it is larger than the sum of its proper divisors (1).

621665549 is an equidigital number, since it uses as much as digits as its factorization.

621665549 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 388800, while the sum is 44.

The square root of 621665549 is about 24933.2217934225. The cubic root of 621665549 is about 853.4647730305.

The spelling of 621665549 in words is "six hundred twenty-one million, six hundred sixty-five thousand, five hundred forty-nine".