409681 has 4 divisors (see below), whose sum is σ = 411700. Its totient is φ = 407664.

The previous prime is 409657. The next prime is 409691. The reversal of 409681 is 186904.

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

It can be written as a sum of positive squares in 2 ways, for example, as 384400 + 25281 = 620^2 + 159^2 .

It is a cyclic number.

It is not a de Polignac number, because 409681 - 2¹¹ = 407633 is a prime.

It is a super-2 number, since 2×409681² = 335677043522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (409691) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 666 + ... + 1123.

It is an arithmetic number, because the mean of its divisors is an integer number (102925).

2⁴⁰⁹⁶⁸¹ is an apocalyptic number.

It is an amenable number.

409681 is a deficient number, since it is larger than the sum of its proper divisors (2019).

409681 is a wasteful number, since it uses less digits than its factorization.

409681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2018.

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 409681 is about 640.0632781218. The cubic root of 409681 is about 74.2703164409.

It can be divided in two parts, 4096 and 81, that multiplied together give a 4-th power (331776 = 24⁴).

The spelling of 409681 in words is "four hundred nine thousand, six hundred eighty-one".