639744541 has 4 divisors (see below), whose sum is σ = 657034972. Its totient is φ = 622454112.

The previous prime is 639744529. The next prime is 639744587. The reversal of 639744541 is 145447936.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 460960900 + 178783641 = 21470^2 + 13371^2 .

It is a cyclic number.

It is not a de Polignac number, because 639744541 - 2²⁹ = 102873629 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (633744541) 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, 8645160 + ... + 8645233.

It is an arithmetic number, because the mean of its divisors is an integer number (164258743).

Almost surely, 2^639744541 is an apocalyptic number.

It is an amenable number.

639744541 is a deficient number, since it is larger than the sum of its proper divisors (17290431).

639744541 is a wasteful number, since it uses less digits than its factorization.

639744541 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17290430.

The product of its digits is 362880, while the sum is 43.

The square root of 639744541 is about 25293.1718256133. The cubic root of 639744541 is about 861.6592003929.

The spelling of 639744541 in words is "six hundred thirty-nine million, seven hundred forty-four thousand, five hundred forty-one".