405640321 has 4 divisors (see below), whose sum is σ = 408736944. Its totient is φ = 402543700.

The previous prime is 405640307. The next prime is 405640337. The reversal of 405640321 is 123046504.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 405640321 - 2²³ = 397251713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (405640421) 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, 1548115 + ... + 1548376.

It is an arithmetic number, because the mean of its divisors is an integer number (102184236).

Almost surely, 2^405640321 is an apocalyptic number.

It is an amenable number.

405640321 is a deficient number, since it is larger than the sum of its proper divisors (3096623).

405640321 is a wasteful number, since it uses less digits than its factorization.

405640321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3096622.

The product of its (nonzero) digits is 2880, while the sum is 25.

The square root of 405640321 is about 20140.5144174621. The cubic root of 405640321 is about 740.2533348596.

Adding to 405640321 its reverse (123046504), we get a palindrome (528686825).

The spelling of 405640321 in words is "four hundred five million, six hundred forty thousand, three hundred twenty-one".