639443641 has 4 divisors (see below), whose sum is σ = 639654400. Its totient is φ = 639232884.

The previous prime is 639443639. The next prime is 639443653. The reversal of 639443641 is 146344936.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 639443641 - 2¹ = 639443639 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 639443594 and 639443603.

It is not an unprimeable number, because it can be changed into a prime (639443611) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 100761 + ... + 106918.

It is an arithmetic number, because the mean of its divisors is an integer number (159913600).

Almost surely, 2^639443641 is an apocalyptic number.

It is an amenable number.

639443641 is a deficient number, since it is larger than the sum of its proper divisors (210759).

639443641 is a wasteful number, since it uses less digits than its factorization.

639443641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 210758.

The product of its digits is 186624, while the sum is 40.

The square root of 639443641 is about 25287.2228803402. Note that the first 3 decimals coincide. The cubic root of 639443641 is about 861.5240871320.

The spelling of 639443641 in words is "six hundred thirty-nine million, four hundred forty-three thousand, six hundred forty-one".