646145021 has 2 divisors, whose sum is σ = 646145022. Its totient is φ = 646145020.

The previous prime is 646145009. The next prime is 646145039. The reversal of 646145021 is 120541646.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 565773796 + 80371225 = 23786^2 + 8965^2 .

It is a cyclic number.

It is not a de Polignac number, because 646145021 - 2¹⁸ = 645882877 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (646145041) 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, 323072510 + 323072511.

It is an arithmetic number, because the mean of its divisors is an integer number (323072511).

Almost surely, 2^646145021 is an apocalyptic number.

It is an amenable number.

646145021 is a deficient number, since it is larger than the sum of its proper divisors (1).

646145021 is an equidigital number, since it uses as much as digits as its factorization.

646145021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5760, while the sum is 29.

The square root of 646145021 is about 25419.3827816491. The cubic root of 646145021 is about 864.5232299731.

Adding to 646145021 its reverse (120541646), we get a palindrome (766686667).

The spelling of 646145021 in words is "six hundred forty-six million, one hundred forty-five thousand, twenty-one".