631809 has 6 divisors (see below), whose sum is σ = 912626. Its totient is φ = 421200.

The previous prime is 631789. The next prime is 631817. The reversal of 631809 is 908136.

It can be written as a sum of positive squares in only one way, i.e., 608400 + 23409 = 780^2 + 153^2 .

It is not a de Polignac number, because 631809 - 2⁷ = 631681 is a prime.

It is a super-2 number, since 2×631809² = 798365224962, which contains 22 as substring.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 631809.

It is not an unprimeable number, because it can be changed into a prime (631819) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 35092 + ... + 35109.

It is a Proth number, since it is equal to 617 ⋅ 2¹⁰ + 1 and 617 < 2¹⁰.

2⁶³¹⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

631809 is a deficient number, since it is larger than the sum of its proper divisors (280817).

631809 is a wasteful number, since it uses less digits than its factorization.

631809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 70207 (or 70204 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 27.

The square root of 631809 is about 794.8641393345. The cubic root of 631809 is about 85.8081626218.

The spelling of 631809 in words is "six hundred thirty-one thousand, eight hundred nine".