405002021 has 4 divisors (see below), whose sum is σ = 409012044. Its totient is φ = 400992000.

The previous prime is 405001981. The next prime is 405002047. The reversal of 405002021 is 120200504.

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 383611396 + 21390625 = 19586^2 + 4625^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-405002021 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 405001987 and 405002005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (405002621) 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, 2004860 + ... + 2005061.

It is an arithmetic number, because the mean of its divisors is an integer number (102253011).

Almost surely, 2^405002021 is an apocalyptic number.

It is an amenable number.

405002021 is a deficient number, since it is larger than the sum of its proper divisors (4010023).

405002021 is a wasteful number, since it uses less digits than its factorization.

405002021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4010022.

The product of its (nonzero) digits is 80, while the sum is 14.

The square root of 405002021 is about 20124.6620095842. The cubic root of 405002021 is about 739.8648529674.

Adding to 405002021 its reverse (120200504), we get a palindrome (525202525).

The spelling of 405002021 in words is "four hundred five million, two thousand, twenty-one".