21131305 has 16 divisors (see below), whose sum is σ = 28191744. Its totient is φ = 15099840.

The previous prime is 21131293. The next prime is 21131317. The reversal of 21131305 is 50313112.

It is an interprime number because it is at equal distance from previous prime (21131293) and next prime (21131317).

It is not a de Polignac number, because 21131305 - 2¹⁷ = 21000233 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3229 + ... + 7258.

It is an arithmetic number, because the mean of its divisors is an integer number (1761984).

Almost surely, 2^21131305 is an apocalyptic number.

It is an amenable number.

21131305 is a deficient number, since it is larger than the sum of its proper divisors (7060439).

21131305 is a wasteful number, since it uses less digits than its factorization.

21131305 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10536.

The product of its (nonzero) digits is 90, while the sum is 16.

The square root of 21131305 is about 4596.8799201197. The cubic root of 21131305 is about 276.4662400589.

Adding to 21131305 its reverse (50313112), we get a palindrome (71444417).

The spelling of 21131305 in words is "twenty-one million, one hundred thirty-one thousand, three hundred five".