21420345 has 16 divisors (see below), whose sum is σ = 34756992. Its totient is φ = 11262720.

The previous prime is 21420331. The next prime is 21420397. The reversal of 21420345 is 54302412.

It is not a de Polignac number, because 21420345 - 2⁶ = 21420281 is a prime.

It is a Curzon number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8992 + ... + 11121.

It is an arithmetic number, because the mean of its divisors is an integer number (2172312).

Almost surely, 2^21420345 is an apocalyptic number.

It is an amenable number.

21420345 is a deficient number, since it is larger than the sum of its proper divisors (13336647).

21420345 is a wasteful number, since it uses less digits than its factorization.

21420345 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20192.

The product of its (nonzero) digits is 960, while the sum is 21.

The square root of 21420345 is about 4628.2118577265. The cubic root of 21420345 is about 277.7210640067.

Adding to 21420345 its reverse (54302412), we get a palindrome (75722757).

The spelling of 21420345 in words is "twenty-one million, four hundred twenty thousand, three hundred forty-five".