21305969 has 4 divisors (see below), whose sum is σ = 21881844. Its totient is φ = 20730096.

The previous prime is 21305939. The next prime is 21305983. The reversal of 21305969 is 96950312.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 18809569 + 2496400 = 4337^2 + 1580^2 .

It is a cyclic number.

It is not a de Polignac number, because 21305969 - 2¹² = 21301873 is a prime.

It is a super-2 number, since 2×21305969² = 907888630057922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21305909) 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 3 ways as a sum of consecutive naturals, for example, 287882 + ... + 287955.

It is an arithmetic number, because the mean of its divisors is an integer number (5470461).

Almost surely, 2^21305969 is an apocalyptic number.

It is an amenable number.

21305969 is a deficient number, since it is larger than the sum of its proper divisors (575875).

21305969 is an equidigital number, since it uses as much as digits as its factorization.

21305969 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 575874.

The product of its (nonzero) digits is 14580, while the sum is 35.

The square root of 21305969 is about 4615.8389269991. The cubic root of 21305969 is about 277.2258754451.

The spelling of 21305969 in words is "twenty-one million, three hundred five thousand, nine hundred sixty-nine".