643697216 has 14 divisors (see below), whose sum is σ = 1277336790. Its totient is φ = 321848576.

The previous prime is 643697213. The next prime is 643697261. The reversal of 643697216 is 612796346.

It can be written as a sum of positive squares in only one way, i.e., 439321600 + 204375616 = 20960^2 + 14296^2 .

It is a super-2 number, since 2×643697216² = 828692211772301312, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (643697213) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5028821 + ... + 5028948.

Almost surely, 2^643697216 is an apocalyptic number.

It is an amenable number.

643697216 is a deficient number, since it is larger than the sum of its proper divisors (633639574).

643697216 is a wasteful number, since it uses less digits than its factorization.

643697216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10057781 (or 10057771 counting only the distinct ones).

The product of its digits is 326592, while the sum is 44.

The square root of 643697216 is about 25371.1886989948. The cubic root of 643697216 is about 863.4301512181.

The spelling of 643697216 in words is "six hundred forty-three million, six hundred ninety-seven thousand, two hundred sixteen".