21618745 has 16 divisors (see below), whose sum is σ = 26496000. Its totient is φ = 16930368.

The previous prime is 21618739. The next prime is 21618787. The reversal of 21618745 is 54781612.

It is a cyclic number.

It is not a de Polignac number, because 21618745 - 2¹¹ = 21616697 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a self number, because there is not a number n which added to its sum of digits gives 21618745.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 90336 + ... + 90574.

It is an arithmetic number, because the mean of its divisors is an integer number (1656000).

Almost surely, 2^21618745 is an apocalyptic number.

It is an amenable number.

21618745 is a deficient number, since it is larger than the sum of its proper divisors (4877255).

21618745 is a wasteful number, since it uses less digits than its factorization.

21618745 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 552.

The product of its digits is 13440, while the sum is 34.

The square root of 21618745 is about 4649.5962190281. The cubic root of 21618745 is about 278.5758683742.

The spelling of 21618745 in words is "twenty-one million, six hundred eighteen thousand, seven hundred forty-five".