21047785 has 16 divisors (see below), whose sum is σ = 29175552. Its totient is φ = 14406400.

The previous prime is 21047777. The next prime is 21047813. The reversal of 21047785 is 58774012.

It is a happy number.

It is not a de Polignac number, because 21047785 - 2³ = 21047777 is a prime.

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 21047785.

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, 10321 + ... + 12190.

It is an arithmetic number, because the mean of its divisors is an integer number (1823472).

Almost surely, 2^21047785 is an apocalyptic number.

It is an amenable number.

21047785 is a deficient number, since it is larger than the sum of its proper divisors (8127767).

21047785 is a wasteful number, since it uses less digits than its factorization.

21047785 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22544.

The product of its (nonzero) digits is 15680, while the sum is 34.

The square root of 21047785 is about 4587.7865033151. The cubic root of 21047785 is about 276.1015213239.

It can be divided in two parts, 2104 and 7785, that added together give a palindrome (9889).

The spelling of 21047785 in words is "twenty-one million, forty-seven thousand, seven hundred eighty-five".