646021247 has 4 divisors (see below), whose sum is σ = 647682360. Its totient is φ = 644360136.

The previous prime is 646021241. The next prime is 646021279. The reversal of 646021247 is 742120646.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 646021247 - 2⁴ = 646021231 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (646021241) 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 in 3 ways as a sum of consecutive naturals, for example, 829973 + ... + 830750.

It is an arithmetic number, because the mean of its divisors is an integer number (161920590).

Almost surely, 2^646021247 is an apocalyptic number.

646021247 is a deficient number, since it is larger than the sum of its proper divisors (1661113).

646021247 is a wasteful number, since it uses less digits than its factorization.

646021247 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1661112.

The product of its (nonzero) digits is 16128, while the sum is 32.

The square root of 646021247 is about 25416.9480268580. The cubic root of 646021247 is about 864.4680244449.

The spelling of 646021247 in words is "six hundred forty-six million, twenty-one thousand, two hundred forty-seven".