21027645 has 24 divisors (see below), whose sum is σ = 37298976. Its totient is φ = 10952928.

The previous prime is 21027637. The next prime is 21027649. The reversal of 21027645 is 54672012.

21027645 is a `hidden beast` number, since 2 + 10 + 2 + 7 + 645 = 666.

It is not a de Polignac number, because 21027645 - 2³ = 21027637 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21027649) 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 23 ways as a sum of consecutive naturals, for example, 3499 + ... + 7368.

It is an arithmetic number, because the mean of its divisors is an integer number (1554124).

Almost surely, 2^21027645 is an apocalyptic number.

It is an amenable number.

21027645 is a deficient number, since it is larger than the sum of its proper divisors (16271331).

21027645 is a wasteful number, since it uses less digits than its factorization.

21027645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10921 (or 10918 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 27.

The square root of 21027645 is about 4585.5910197051. The cubic root of 21027645 is about 276.0134287732.

Adding to 21027645 its reverse (54672012), we get a palindrome (75699657).

The spelling of 21027645 in words is "twenty-one million, twenty-seven thousand, six hundred forty-five".