21405313 has 2 divisors, whose sum is σ = 21405314. Its totient is φ = 21405312.

The previous prime is 21405299. The next prime is 21405337. The reversal of 21405313 is 31350412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14265729 + 7139584 = 3777^2 + 2672^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21405313 is a prime.

It is not a weakly prime, because it can be changed into another prime (21405383) 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 as a sum of consecutive naturals, namely, 10702656 + 10702657.

It is an arithmetic number, because the mean of its divisors is an integer number (10702657).

Almost surely, 2^21405313 is an apocalyptic number.

It is an amenable number.

21405313 is a deficient number, since it is larger than the sum of its proper divisors (1).

21405313 is an equidigital number, since it uses as much as digits as its factorization.

21405313 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 360, while the sum is 19.

The square root of 21405313 is about 4626.5876194016. The cubic root of 21405313 is about 277.6560840393.

Adding to 21405313 its reverse (31350412), we get a palindrome (52755725).

The spelling of 21405313 in words is "twenty-one million, four hundred five thousand, three hundred thirteen".