642346021 has 2 divisors, whose sum is σ = 642346022. Its totient is φ = 642346020.

The previous prime is 642345989. The next prime is 642346031. The reversal of 642346021 is 120643246.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 629457921 + 12888100 = 25089^2 + 3590^2 .

It is a cyclic number.

It is not a de Polignac number, because 642346021 - 2⁵ = 642345989 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (642346031) 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, 321173010 + 321173011.

It is an arithmetic number, because the mean of its divisors is an integer number (321173011).

Almost surely, 2^642346021 is an apocalyptic number.

It is an amenable number.

642346021 is a deficient number, since it is larger than the sum of its proper divisors (1).

642346021 is an equidigital number, since it uses as much as digits as its factorization.

642346021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6912, while the sum is 28.

The square root of 642346021 is about 25344.5461786160. The cubic root of 642346021 is about 862.8255813741.

Adding to 642346021 its reverse (120643246), we get a palindrome (762989267).

The spelling of 642346021 in words is "six hundred forty-two million, three hundred forty-six thousand, twenty-one".