21451305 has 16 divisors (see below), whose sum is σ = 35250624. Its totient is φ = 11131200.

The previous prime is 21451303. The next prime is 21451307. The reversal of 21451305 is 50315412.

It is an interprime number because it is at equal distance from previous prime (21451303) and next prime (21451307).

It is not a de Polignac number, because 21451305 - 2¹ = 21451303 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21451303) 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 in 15 ways as a sum of consecutive naturals, for example, 18771 + ... + 19880.

It is an arithmetic number, because the mean of its divisors is an integer number (2203164).

Almost surely, 2^21451305 is an apocalyptic number.

It is an amenable number.

21451305 is a deficient number, since it is larger than the sum of its proper divisors (13799319).

21451305 is a wasteful number, since it uses less digits than its factorization.

21451305 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38696.

The product of its (nonzero) digits is 600, while the sum is 21.

The square root of 21451305 is about 4631.5553543059. Note that the first 3 decimals coincide. The cubic root of 21451305 is about 277.8548014257.

Adding to 21451305 its reverse (50315412), we get a palindrome (71766717).

The spelling of 21451305 in words is "twenty-one million, four hundred fifty-one thousand, three hundred five".