40639 has 2 divisors, whose sum is σ = 40640. Its totient is φ = 40638.

The previous prime is 40637. The next prime is 40693. The reversal of 40639 is 93604.

Together with next prime (40693) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 40639 - 2¹ = 40637 is a prime.

Together with 40637, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (40637) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20319 + 20320.

It is an arithmetic number, because the mean of its divisors is an integer number (20320).

2⁴⁰⁶³⁹ is an apocalyptic number.

40639 is a deficient number, since it is larger than the sum of its proper divisors (1).

40639 is an equidigital number, since it uses as much as digits as its factorization.

40639 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 648, while the sum is 22.

The square root of 40639 is about 201.5911704416. The cubic root of 40639 is about 34.3806701390.

The spelling of 40639 in words is "forty thousand, six hundred thirty-nine".