631639 has 4 divisors (see below), whose sum is σ = 633424. Its totient is φ = 629856.

The previous prime is 631619. The next prime is 631643. The reversal of 631639 is 936136.

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

It is a 5-Lehmer number, since φ(631639) divides (631639-1)⁵.

It is a cyclic number.

It is not a de Polignac number, because 631639 - 2¹¹ = 629591 is a prime.

It is a Duffinian number.

631639 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (631619) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 162 + ... + 1135.

It is an arithmetic number, because the mean of its divisors is an integer number (158356).

2⁶³¹⁶³⁹ is an apocalyptic number.

631639 is a deficient number, since it is larger than the sum of its proper divisors (1785).

631639 is a wasteful number, since it uses less digits than its factorization.

631639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1784.

The product of its digits is 2916, while the sum is 28.

The square root of 631639 is about 794.7571956264. The cubic root of 631639 is about 85.8004658357.

The spelling of 631639 in words is "six hundred thirty-one thousand, six hundred thirty-nine".