21185745 has 16 divisors (see below), whose sum is σ = 38739840. Its totient is φ = 9684864.

The previous prime is 21185729. The next prime is 21185771. The reversal of 21185745 is 54758112.

It is not a de Polignac number, because 21185745 - 2⁴ = 21185729 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 100780 + ... + 100989.

It is an arithmetic number, because the mean of its divisors is an integer number (2421240).

Almost surely, 2^21185745 is an apocalyptic number.

It is an amenable number.

21185745 is a deficient number, since it is larger than the sum of its proper divisors (17554095).

21185745 is a wasteful number, since it uses less digits than its factorization.

21185745 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 201784.

The product of its digits is 11200, while the sum is 33.

The square root of 21185745 is about 4602.7975189009. The cubic root of 21185745 is about 276.7034539235.

The spelling of 21185745 in words is "twenty-one million, one hundred eighty-five thousand, seven hundred forty-five".