21253785 has 32 divisors (see below), whose sum is σ = 39820032. Its totient is φ = 9477120.

The previous prime is 21253763. The next prime is 21253849. The reversal of 21253785 is 58735212.

21253785 = T₃₄₉ + T₃₅₀ + ... + T₅₅₃.

It is not a de Polignac number, because 21253785 - 2⁶ = 21253721 is a prime.

It is a Curzon number.

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 31 ways as a sum of consecutive naturals, for example, 1837 + ... + 6773.

It is an arithmetic number, because the mean of its divisors is an integer number (1244376).

Almost surely, 2^21253785 is an apocalyptic number.

It is an amenable number.

21253785 is a deficient number, since it is larger than the sum of its proper divisors (18566247).

21253785 is a wasteful number, since it uses less digits than its factorization.

21253785 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4993.

The product of its digits is 16800, while the sum is 33.

The square root of 21253785 is about 4610.1827512583. The cubic root of 21253785 is about 276.9993570430. Note that the first 3 decimals are identical.

Adding to 21253785 its reverse (58735212), we get a palindrome (79988997).

The spelling of 21253785 in words is "twenty-one million, two hundred fifty-three thousand, seven hundred eighty-five".