646500002021 has 2 divisors, whose sum is σ = 646500002022. Its totient is φ = 646500002020.

The previous prime is 646500001949. The next prime is 646500002039. The reversal of 646500002021 is 120200005646.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 639592065025 + 6907936996 = 799745^2 + 83114^2 .

It is a cyclic number.

It is not a de Polignac number, because 646500002021 - 2³⁸ = 371622095077 is a prime.

It is a super-2 number, since 2×646500002021² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (646500032021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323250001010 + 323250001011.

It is an arithmetic number, because the mean of its divisors is an integer number (323250001011).

Almost surely, 2^646500002021 is an apocalyptic number.

It is an amenable number.

646500002021 is a deficient number, since it is larger than the sum of its proper divisors (1).

646500002021 is an equidigital number, since it uses as much as digits as its factorization.

646500002021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2880, while the sum is 26.

Adding to 646500002021 its reverse (120200005646), we get a palindrome (766700007667).

The spelling of 646500002021 in words is "six hundred forty-six billion, five hundred million, two thousand, twenty-one".