21305069 has 4 divisors (see below), whose sum is σ = 21384540. Its totient is φ = 21225600.

The previous prime is 21305059. The next prime is 21305071. The reversal of 21305069 is 96050312.

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 9229444 + 12075625 = 3038^2 + 3475^2 .

It is a cyclic number.

It is not a de Polignac number, because 21305069 - 2¹² = 21300973 is a prime.

It is a super-2 number, since 2×21305069² = 907811930189522, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21305059) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 39332 + ... + 39869.

It is an arithmetic number, because the mean of its divisors is an integer number (5346135).

Almost surely, 2^21305069 is an apocalyptic number.

It is an amenable number.

21305069 is a deficient number, since it is larger than the sum of its proper divisors (79471).

21305069 is an equidigital number, since it uses as much as digits as its factorization.

21305069 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79470.

The product of its (nonzero) digits is 1620, while the sum is 26.

The square root of 21305069 is about 4615.7414355659. The cubic root of 21305069 is about 277.2219718943.

The spelling of 21305069 in words is "twenty-one million, three hundred five thousand, sixty-nine".