21392305 has 16 divisors (see below), whose sum is σ = 28289088. Its totient is φ = 15400000.

The previous prime is 21392303. The next prime is 21392317. The reversal of 21392305 is 50329312.

It is a happy number.

It is not a de Polignac number, because 21392305 - 2¹ = 21392303 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21392305.

It is not an unprimeable number, because it can be changed into a prime (21392303) by changing a digit.

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, 3630 + ... + 7480.

It is an arithmetic number, because the mean of its divisors is an integer number (1768068).

Almost surely, 2^21392305 is an apocalyptic number.

It is an amenable number.

21392305 is a deficient number, since it is larger than the sum of its proper divisors (6896783).

21392305 is a wasteful number, since it uses less digits than its factorization.

21392305 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3968.

The product of its (nonzero) digits is 1620, while the sum is 25.

The square root of 21392305 is about 4625.1816180557. The cubic root of 21392305 is about 277.5998288125.

It can be divided in two parts, 2139 and 2305, that added together give a palindrome (4444).

The spelling of 21392305 in words is "twenty-one million, three hundred ninety-two thousand, three hundred five".