405640421 has 2 divisors, whose sum is σ = 405640422. Its totient is φ = 405640420.

The previous prime is 405640393. The next prime is 405640439. The reversal of 405640421 is 124046504.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 404452321 + 1188100 = 20111^2 + 1090^2 .

It is a cyclic number.

It is not a de Polignac number, because 405640421 - 2⁶ = 405640357 is a prime.

It is a super-2 number, since 2×405640421² = 329088302298114482, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (405640441) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 202820210 + 202820211.

It is an arithmetic number, because the mean of its divisors is an integer number (202820211).

Almost surely, 2^405640421 is an apocalyptic number.

It is an amenable number.

405640421 is a deficient number, since it is larger than the sum of its proper divisors (1).

405640421 is an equidigital number, since it uses as much as digits as its factorization.

405640421 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3840, while the sum is 26.

The square root of 405640421 is about 20140.5169000202. The cubic root of 405640421 is about 740.2533956896.

Adding to 405640421 its reverse (124046504), we get a palindrome (529686925).

The spelling of 405640421 in words is "four hundred five million, six hundred forty thousand, four hundred twenty-one".