405740021 has 2 divisors, whose sum is σ = 405740022. Its totient is φ = 405740020.

The previous prime is 405740011. The next prime is 405740047. The reversal of 405740021 is 120047504.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 388641796 + 17098225 = 19714^2 + 4135^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-405740021 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (405740011) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 202870010 + 202870011.

It is an arithmetic number, because the mean of its divisors is an integer number (202870011).

Almost surely, 2^405740021 is an apocalyptic number.

It is an amenable number.

405740021 is a deficient number, since it is larger than the sum of its proper divisors (1).

405740021 is an equidigital number, since it uses as much as digits as its factorization.

405740021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1120, while the sum is 23.

The square root of 405740021 is about 20142.9893759591. The cubic root of 405740021 is about 740.3139774272.

Adding to 405740021 its reverse (120047504), we get a palindrome (525787525).

The spelling of 405740021 in words is "four hundred five million, seven hundred forty thousand, twenty-one".