21254785 has 4 divisors (see below), whose sum is σ = 25505748. Its totient is φ = 17003824.

The previous prime is 21254729. The next prime is 21254789. The reversal of 21254785 is 58745212.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 15437041 + 5817744 = 3929^2 + 2412^2 .

It is a cyclic number.

It is not a de Polignac number, because 21254785 - 2⁹ = 21254273 is a prime.

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

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21254785.

It is not an unprimeable number, because it can be changed into a prime (21254789) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2125474 + ... + 2125483.

It is an arithmetic number, because the mean of its divisors is an integer number (6376437).

Almost surely, 2^21254785 is an apocalyptic number.

It is an amenable number.

21254785 is a deficient number, since it is larger than the sum of its proper divisors (4250963).

21254785 is an equidigital number, since it uses as much as digits as its factorization.

21254785 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4250962.

The product of its digits is 22400, while the sum is 34.

The square root of 21254785 is about 4610.2912055531. The cubic root of 21254785 is about 277.0037012890.

Adding to 21254785 its reverse (58745212), we get a palindrome (79999997).

The spelling of 21254785 in words is "twenty-one million, two hundred fifty-four thousand, seven hundred eighty-five".