21289645 has 16 divisors (see below), whose sum is σ = 27740160. Its totient is φ = 15591744.

The previous prime is 21289643. The next prime is 21289669. The reversal of 21289645 is 54698212.

It is a cyclic number.

It is not a de Polignac number, because 21289645 - 2¹ = 21289643 is a prime.

It is a super-3 number, since 3×21289645³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21289643) 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 15 ways as a sum of consecutive naturals, for example, 6966 + ... + 9544.

It is an arithmetic number, because the mean of its divisors is an integer number (1733760).

Almost surely, 2^21289645 is an apocalyptic number.

It is an amenable number.

21289645 is a deficient number, since it is larger than the sum of its proper divisors (6450515).

21289645 is a wasteful number, since it uses less digits than its factorization.

21289645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2724.

The product of its digits is 34560, while the sum is 37.

The square root of 21289645 is about 4614.0703288962. The cubic root of 21289645 is about 277.1550566144.

The spelling of 21289645 in words is "twenty-one million, two hundred eighty-nine thousand, six hundred forty-five".