402809 has 6 divisors (see below), whose sum is σ = 442890. Its totient is φ = 366080.

The previous prime is 402803. The next prime is 402817. The reversal of 402809 is 908204.

It can be written as a sum of positive squares in only one way, i.e., 327184 + 75625 = 572^2 + 275^2 .

It is a de Polignac number, because none of the positive numbers 2^k-402809 is a prime.

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 402809.

It is not an unprimeable number, because it can be changed into a prime (402803) 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, 1544 + ... + 1785.

It is an arithmetic number, because the mean of its divisors is an integer number (73815).

2⁴⁰²⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

402809 is a deficient number, since it is larger than the sum of its proper divisors (40081).

402809 is a wasteful number, since it uses less digits than its factorization.

402809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3351 (or 3340 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 402809 is about 634.6723564171. The cubic root of 402809 is about 73.8527018822.

The spelling of 402809 in words is "four hundred two thousand, eight hundred nine".