21036309 has 16 divisors (see below), whose sum is σ = 32123520. Its totient is φ = 11995200.

The previous prime is 21036299. The next prime is 21036311. The reversal of 21036309 is 90363012.

It is not a de Polignac number, because 21036309 - 2⁹ = 21035797 is a prime.

It is an alternating number because its digits alternate between even and odd.

21036309 is a modest number, since divided by 6309 gives 2103 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21036409) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 14007 + ... + 15435.

It is an arithmetic number, because the mean of its divisors is an integer number (2007720).

Almost surely, 2^21036309 is an apocalyptic number.

It is an amenable number.

21036309 is a deficient number, since it is larger than the sum of its proper divisors (11087211).

21036309 is a wasteful number, since it uses less digits than its factorization.

21036309 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2140.

The product of its (nonzero) digits is 972, while the sum is 24.

The square root of 21036309 is about 4586.5356207055. The cubic root of 21036309 is about 276.0513320823.

The spelling of 21036309 in words is "twenty-one million, thirty-six thousand, three hundred nine".