21428069 has 8 divisors (see below), whose sum is σ = 23700600. Its totient is φ = 19244736.

The previous prime is 21428051. The next prime is 21428081. The reversal of 21428069 is 96082412.

It can be written as a sum of positive squares in 4 ways, for example, as 1060900 + 20367169 = 1030^2 + 4513^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21428069 - 2¹⁶ = 21362533 is a prime.

It is a super-3 number, since 3×21428069³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21428009) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 21794 + ... + 22755.

It is an arithmetic number, because the mean of its divisors is an integer number (2962575).

Almost surely, 2^21428069 is an apocalyptic number.

It is an amenable number.

21428069 is a deficient number, since it is larger than the sum of its proper divisors (2272531).

21428069 is a wasteful number, since it uses less digits than its factorization.

21428069 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44599.

The product of its (nonzero) digits is 6912, while the sum is 32.

The square root of 21428069 is about 4629.0462300565. The cubic root of 21428069 is about 277.7544413047.

The spelling of 21428069 in words is "twenty-one million, four hundred twenty-eight thousand, sixty-nine".