621543661 has 2 divisors, whose sum is σ = 621543662. Its totient is φ = 621543660.

The previous prime is 621543653. The next prime is 621543677. The reversal of 621543661 is 166345126.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 506925225 + 114618436 = 22515^2 + 10706^2 .

It is a cyclic number.

It is not a de Polignac number, because 621543661 - 2³ = 621543653 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (621543361) 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 as a sum of consecutive naturals, namely, 310771830 + 310771831.

It is an arithmetic number, because the mean of its divisors is an integer number (310771831).

Almost surely, 2^621543661 is an apocalyptic number.

It is an amenable number.

621543661 is a deficient number, since it is larger than the sum of its proper divisors (1).

621543661 is an equidigital number, since it uses as much as digits as its factorization.

621543661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 25920, while the sum is 34.

The square root of 621543661 is about 24930.7773845903. Note that the first 3 decimals coincide. The cubic root of 621543661 is about 853.4089906708.

Adding to 621543661 its reverse (166345126), we get a palindrome (787888787).

The spelling of 621543661 in words is "six hundred twenty-one million, five hundred forty-three thousand, six hundred sixty-one".