639743421 has 8 divisors (see below), whose sum is σ = 861785344. Its totient is φ = 422098560.

The previous prime is 639743407. The next prime is 639743453. The reversal of 639743421 is 124347936.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 639743421 - 2¹⁸ = 639481277 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 639743421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639743491) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1098925 + ... + 1099506.

It is an arithmetic number, because the mean of its divisors is an integer number (107723168).

Almost surely, 2^639743421 is an apocalyptic number.

It is an amenable number.

639743421 is a deficient number, since it is larger than the sum of its proper divisors (222041923).

639743421 is a wasteful number, since it uses less digits than its factorization.

639743421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2198531.

The product of its digits is 108864, while the sum is 39.

The square root of 639743421 is about 25293.1496852409. The cubic root of 639743421 is about 861.6586975574.

The spelling of 639743421 in words is "six hundred thirty-nine million, seven hundred forty-three thousand, four hundred twenty-one".