405405021 has 16 divisors (see below), whose sum is σ = 618467328. Its totient is φ = 231394800.

The previous prime is 405405017. The next prime is 405405023. The reversal of 405405021 is 120504504.

It is not a de Polignac number, because 405405021 - 2² = 405405017 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (405405023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8536 + ... + 29726.

It is an arithmetic number, because the mean of its divisors is an integer number (38654208).

Almost surely, 2^405405021 is an apocalyptic number.

It is an amenable number.

405405021 is a deficient number, since it is larger than the sum of its proper divisors (213062307).

405405021 is a wasteful number, since it uses less digits than its factorization.

405405021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22112.

The product of its (nonzero) digits is 800, while the sum is 21.

The square root of 405405021 is about 20134.6721105659. The cubic root of 405405021 is about 740.1101741244.

Adding to 405405021 its reverse (120504504), we get a palindrome (525909525).

The spelling of 405405021 in words is "four hundred five million, four hundred five thousand, twenty-one".