643239081 has 24 divisors (see below), whose sum is σ = 988817544. Its totient is φ = 401533440.

The previous prime is 643239059. The next prime is 643239089. The reversal of 643239081 is 180932346.

643239081 is a `hidden beast` number, since 643 + 2 + 3 + 9 + 0 + 8 + 1 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 567392400 + 75846681 = 23820^2 + 8709^2 .

It is not a de Polignac number, because 643239081 - 2⁵ = 643239049 is a prime.

It is a super-2 number, since 2×643239081² = 827513030651449122, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (643239089) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 19471 + ... + 40811.

It is an arithmetic number, because the mean of its divisors is an integer number (41200731).

Almost surely, 2^643239081 is an apocalyptic number.

It is an amenable number.

643239081 is a deficient number, since it is larger than the sum of its proper divisors (345578463).

643239081 is a wasteful number, since it uses less digits than its factorization.

643239081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21561 (or 21558 counting only the distinct ones).

The product of its (nonzero) digits is 31104, while the sum is 36.

The square root of 643239081 is about 25362.1584452112. The cubic root of 643239081 is about 863.2252611731.

The spelling of 643239081 in words is "six hundred forty-three million, two hundred thirty-nine thousand, eighty-one".