21856785 has 16 divisors (see below), whose sum is σ = 36491904. Its totient is φ = 11149952.

The previous prime is 21856763. The next prime is 21856801. The reversal of 21856785 is 58765812.

It is a cyclic number.

It is not a de Polignac number, because 21856785 - 2⁷ = 21856657 is a prime.

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

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, 31332 + ... + 32021.

It is an arithmetic number, because the mean of its divisors is an integer number (2280744).

Almost surely, 2^21856785 is an apocalyptic number.

It is an amenable number.

21856785 is a deficient number, since it is larger than the sum of its proper divisors (14635119).

21856785 is a wasteful number, since it uses less digits than its factorization.

21856785 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 63384.

The product of its digits is 134400, while the sum is 42.

The square root of 21856785 is about 4675.1240625250. The cubic root of 21856785 is about 279.5945876059.

The spelling of 21856785 in words is "twenty-one million, eight hundred fifty-six thousand, seven hundred eighty-five".