646641901 has 2 divisors, whose sum is σ = 646641902. Its totient is φ = 646641900.

The previous prime is 646641899. The next prime is 646641959. The reversal of 646641901 is 109146646.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 558187876 + 88454025 = 23626^2 + 9405^2 .

It is a cyclic number.

It is not a de Polignac number, because 646641901 - 2¹ = 646641899 is a prime.

Together with 646641899, 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 (646641601) 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, 323320950 + 323320951.

It is an arithmetic number, because the mean of its divisors is an integer number (323320951).

Almost surely, 2^646641901 is an apocalyptic number.

It is an amenable number.

646641901 is a deficient number, since it is larger than the sum of its proper divisors (1).

646641901 is an equidigital number, since it uses as much as digits as its factorization.

646641901 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 31104, while the sum is 37.

The square root of 646641901 is about 25429.1545474874. The cubic root of 646641901 is about 864.7447768525.

The spelling of 646641901 in words is "six hundred forty-six million, six hundred forty-one thousand, nine hundred one".