643551121 has 2 divisors, whose sum is σ = 643551122. Its totient is φ = 643551120.

The previous prime is 643551113. The next prime is 643551127. The reversal of 643551121 is 121155346.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 383180625 + 260370496 = 19575^2 + 16136^2 .

It is a cyclic number.

It is not a de Polignac number, because 643551121 - 2³ = 643551113 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 643551121.

It is not a weakly prime, because it can be changed into another prime (643551127) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321775560 + 321775561.

It is an arithmetic number, because the mean of its divisors is an integer number (321775561).

Almost surely, 2^643551121 is an apocalyptic number.

It is an amenable number.

643551121 is a deficient number, since it is larger than the sum of its proper divisors (1).

643551121 is an equidigital number, since it uses as much as digits as its factorization.

643551121 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3600, while the sum is 28.

The square root of 643551121 is about 25368.3093839538. The cubic root of 643551121 is about 863.3648242448.

The spelling of 643551121 in words is "six hundred forty-three million, five hundred fifty-one thousand, one hundred twenty-one".