646378221 has 8 divisors (see below), whose sum is σ = 870722944. Its totient is φ = 426476160.

The previous prime is 646378207. The next prime is 646378259. The reversal of 646378221 is 122873646.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 646378221 - 2¹⁸ = 646116077 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 646378221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (646378121) 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 in 7 ways as a sum of consecutive naturals, for example, 1110325 + ... + 1110906.

It is an arithmetic number, because the mean of its divisors is an integer number (108840368).

Almost surely, 2^646378221 is an apocalyptic number.

It is an amenable number.

646378221 is a deficient number, since it is larger than the sum of its proper divisors (224344723).

646378221 is a wasteful number, since it uses less digits than its factorization.

646378221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2221331.

The product of its digits is 96768, while the sum is 39.

The square root of 646378221 is about 25423.9694186411. The cubic root of 646378221 is about 864.6272224008.

The spelling of 646378221 in words is "six hundred forty-six million, three hundred seventy-eight thousand, two hundred twenty-one".