646360021 has 2 divisors, whose sum is σ = 646360022. Its totient is φ = 646360020.

The previous prime is 646360019. The next prime is 646360049. The reversal of 646360021 is 120063646.

It is an a-pointer prime, because the next prime (646360049) can be obtained adding 646360021 to its sum of digits (28).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 599711121 + 46648900 = 24489^2 + 6830^2 .

It is a cyclic number.

It is not a de Polignac number, because 646360021 - 2¹ = 646360019 is a prime.

Together with 646360019, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (646360061) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323180010 + 323180011.

It is an arithmetic number, because the mean of its divisors is an integer number (323180011).

Almost surely, 2^646360021 is an apocalyptic number.

It is an amenable number.

646360021 is a deficient number, since it is larger than the sum of its proper divisors (1).

646360021 is an equidigital number, since it uses as much as digits as its factorization.

646360021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5184, while the sum is 28.

The square root of 646360021 is about 25423.6114861756. The cubic root of 646360021 is about 864.6191072536.

The spelling of 646360021 in words is "six hundred forty-six million, three hundred sixty thousand, twenty-one".