21375813 has 16 divisors (see below), whose sum is σ = 29623680. Its totient is φ = 13694016.

The previous prime is 21375811. The next prime is 21375821. The reversal of 21375813 is 31857312.

It is not a de Polignac number, because 21375813 - 2¹ = 21375811 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21375811) 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, 23656 + ... + 24542.

It is an arithmetic number, because the mean of its divisors is an integer number (1851480).

Almost surely, 2^21375813 is an apocalyptic number.

It is an amenable number.

21375813 is a deficient number, since it is larger than the sum of its proper divisors (8247867).

21375813 is a wasteful number, since it uses less digits than its factorization.

21375813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1196.

The product of its digits is 5040, while the sum is 30.

The square root of 21375813 is about 4623.3984254010. The cubic root of 21375813 is about 277.5284736630.

The spelling of 21375813 in words is "twenty-one million, three hundred seventy-five thousand, eight hundred thirteen".