646979521 has 8 divisors (see below), whose sum is σ = 664849064. Its totient is φ = 629130240.

The previous prime is 646979519. The next prime is 646979539. The reversal of 646979521 is 125979646.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 101103025 + 545876496 = 10055^2 + 23364^2 .

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

It is not a de Polignac number, because 646979521 - 2¹ = 646979519 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (646977521) 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 7 ways as a sum of consecutive naturals, for example, 78241 + ... + 86113.

It is an arithmetic number, because the mean of its divisors is an integer number (83106133).

Almost surely, 2^646979521 is an apocalyptic number.

It is an amenable number.

646979521 is a deficient number, since it is larger than the sum of its proper divisors (17869543).

646979521 is a wasteful number, since it uses less digits than its factorization.

646979521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10131.

The product of its digits is 816480, while the sum is 49.

The square root of 646979521 is about 25435.7921244847. The cubic root of 646979521 is about 864.8952487673.

The spelling of 646979521 in words is "six hundred forty-six million, nine hundred seventy-nine thousand, five hundred twenty-one".