21310509 has 16 divisors (see below), whose sum is σ = 31074624. Its totient is φ = 12883200.

The previous prime is 21310493. The next prime is 21310517. The reversal of 21310509 is 90501312.

It is not a de Polignac number, because 21310509 - 2⁴ = 21310493 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21310519) 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, 23749 + ... + 24629.

It is an arithmetic number, because the mean of its divisors is an integer number (1942164).

Almost surely, 2^21310509 is an apocalyptic number.

It is an amenable number.

21310509 is a deficient number, since it is larger than the sum of its proper divisors (9764115).

21310509 is a wasteful number, since it uses less digits than its factorization.

21310509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1628.

The product of its (nonzero) digits is 270, while the sum is 21.

The square root of 21310509 is about 4616.3306857287. The cubic root of 21310509 is about 277.2455650149.

The spelling of 21310509 in words is "twenty-one million, three hundred ten thousand, five hundred nine".