21420245 has 64 divisors (see below), whose sum is σ = 34836480. Its totient is φ = 12249600.

The previous prime is 21420233. The next prime is 21420251. The reversal of 21420245 is 54202412.

It is a happy number.

It is not a de Polignac number, because 21420245 - 2²⁰ = 20371669 is a prime.

It is a Curzon number.

It is a congruent 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 63 ways as a sum of consecutive naturals, for example, 363026 + ... + 363084.

It is an arithmetic number, because the mean of its divisors is an integer number (544320).

Almost surely, 2^21420245 is an apocalyptic number.

It is an amenable number.

21420245 is a deficient number, since it is larger than the sum of its proper divisors (13416235).

21420245 is a wasteful number, since it uses less digits than its factorization.

21420245 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 146.

The product of its (nonzero) digits is 640, while the sum is 20.

The square root of 21420245 is about 4628.2010544055. The cubic root of 21420245 is about 277.7206318296.

Adding to 21420245 its reverse (54202412), we get a palindrome (75622657).

The spelling of 21420245 in words is "twenty-one million, four hundred twenty thousand, two hundred forty-five".