643916061 has 50 divisors (see below), whose sum is σ = 1031982622. Its totient is φ = 400016880.

The previous prime is 643916059. The next prime is 643916071. The reversal of 643916061 is 160619346.

643916061 is a `hidden beast` number, since 6 + 43 + 9 + 1 + 606 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 380016036 + 263900025 = 19494^2 + 16245^2 .

It is not a de Polignac number, because 643916061 - 2¹ = 643916059 is a prime.

It is a super-2 number, since 2×643916061² = 829255787227511442, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643916011) 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 49 ways as a sum of consecutive naturals, for example, 10555971 + ... + 10556031.

Almost surely, 2^643916061 is an apocalyptic number.

643916061 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

It is an amenable number.

643916061 is a deficient number, since it is larger than the sum of its proper divisors (388066561).

643916061 is an frugal number, since it uses more digits than its factorization.

643916061 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 149 (or 83 counting only the distinct ones).

The product of its (nonzero) digits is 23328, while the sum is 36.

The square root of 643916061 is about 25375.5011970207. The cubic root of 643916061 is about 863.5279901589.

It can be divided in two parts, 6439 and 16061, that added together give a square (22500 = 150²).

The spelling of 643916061 in words is "six hundred forty-three million, nine hundred sixteen thousand, sixty-one".