641909993 has 2 divisors, whose sum is σ = 641909994. Its totient is φ = 641909992.

The previous prime is 641909971. The next prime is 641909999. The reversal of 641909993 is 399909146.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 474673369 + 167236624 = 21787^2 + 12932^2 .

It is a cyclic number.

It is not a de Polignac number, because 641909993 - 2¹⁶ = 641844457 is a prime.

It is a super-2 number, since 2×641909993² = 824096878226520098, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (641909999) 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 as a sum of consecutive naturals, namely, 320954996 + 320954997.

It is an arithmetic number, because the mean of its divisors is an integer number (320954997).

Almost surely, 2^641909993 is an apocalyptic number.

It is an amenable number.

641909993 is a deficient number, since it is larger than the sum of its proper divisors (1).

641909993 is an equidigital number, since it uses as much as digits as its factorization.

641909993 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 472392, while the sum is 50.

The square root of 641909993 is about 25335.9427099131. The cubic root of 641909993 is about 862.6303069382.

The spelling of 641909993 in words is "six hundred forty-one million, nine hundred nine thousand, nine hundred ninety-three".