21047685 has 16 divisors (see below), whose sum is σ = 33791424. Its totient is φ = 11187072.

The previous prime is 21047671. The next prime is 21047713. The reversal of 21047685 is 58674012.

It is not a de Polignac number, because 21047685 - 2⁴ = 21047669 is a prime.

It is a congruent number.

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, 2454 + ... + 6936.

It is an arithmetic number, because the mean of its divisors is an integer number (2111964).

Almost surely, 2^21047685 is an apocalyptic number.

It is an amenable number.

21047685 is a deficient number, since it is larger than the sum of its proper divisors (12743739).

21047685 is a wasteful number, since it uses less digits than its factorization.

21047685 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4804.

The product of its (nonzero) digits is 13440, while the sum is 33.

The square root of 21047685 is about 4587.7756048002. The cubic root of 21047685 is about 276.1010840618.

It can be divided in two parts, 210 and 47685, that added together give a triangular number (47895 = T₃₀₉).

The spelling of 21047685 in words is "twenty-one million, forty-seven thousand, six hundred eighty-five".