21685045 has 8 divisors (see below), whose sum is σ = 26212824. Its totient is φ = 17220864.

The previous prime is 21685007. The next prime is 21685049. The reversal of 21685045 is 54058612.

It can be written as a sum of positive squares in 4 ways, for example, as 2692881 + 18992164 = 1641^2 + 4358^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21685045 - 2⁷ = 21684917 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21684998 and 21685016.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21685049) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15144 + ... + 16513.

It is an arithmetic number, because the mean of its divisors is an integer number (3276603).

Almost surely, 2^21685045 is an apocalyptic number.

It is an amenable number.

21685045 is a deficient number, since it is larger than the sum of its proper divisors (4527779).

21685045 is a wasteful number, since it uses less digits than its factorization.

21685045 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31799.

The product of its (nonzero) digits is 9600, while the sum is 31.

The square root of 21685045 is about 4656.7204124792. The cubic root of 21685045 is about 278.8603549998.

The spelling of 21685045 in words is "twenty-one million, six hundred eighty-five thousand, forty-five".