21072645 has 24 divisors (see below), whose sum is σ = 39847392. Its totient is φ = 10216800.

The previous prime is 21072629. The next prime is 21072659. The reversal of 21072645 is 54627012.

21072645 is a `hidden beast` number, since 2 + 10 + 7 + 2 + 645 = 666.

It is not a de Polignac number, because 21072645 - 2⁴ = 21072629 is a prime.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 20791 + ... + 21780.

It is an arithmetic number, because the mean of its divisors is an integer number (1660308).

Almost surely, 2^21072645 is an apocalyptic number.

It is an amenable number.

21072645 is a deficient number, since it is larger than the sum of its proper divisors (18774747).

21072645 is a wasteful number, since it uses less digits than its factorization.

21072645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42593 (or 42590 counting only the distinct ones).

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

The square root of 21072645 is about 4590.4950713403. The cubic root of 21072645 is about 276.2101817400.

Adding to 21072645 its reverse (54627012), we get a palindrome (75699657).

The spelling of 21072645 in words is "twenty-one million, seventy-two thousand, six hundred forty-five".