405721 has 4 divisors (see below), whose sum is σ = 407092. Its totient is φ = 404352.

The previous prime is 405719. The next prime is 405731. The reversal of 405721 is 127504.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 32400 + 373321 = 180^2 + 611^2 .

It is a cyclic number.

It is not a de Polignac number, because 405721 - 2¹ = 405719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (405701) 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, 36 + ... + 901.

It is an arithmetic number, because the mean of its divisors is an integer number (101773).

2⁴⁰⁵⁷²¹ is an apocalyptic number.

It is an amenable number.

405721 is a deficient number, since it is larger than the sum of its proper divisors (1371).

405721 is an equidigital number, since it uses as much as digits as its factorization.

405721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1370.

The product of its (nonzero) digits is 280, while the sum is 19.

The square root of 405721 is about 636.9623222766. The cubic root of 405721 is about 74.0302408663.

The spelling of 405721 in words is "four hundred five thousand, seven hundred twenty-one".