21682985 has 4 divisors (see below), whose sum is σ = 26019588. Its totient is φ = 17346384.

The previous prime is 21682979. The next prime is 21682987. The reversal of 21682985 is 58928612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2226064 + 19456921 = 1492^2 + 4411^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21682985 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21682987) 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 3 ways as a sum of consecutive naturals, for example, 2168294 + ... + 2168303.

It is an arithmetic number, because the mean of its divisors is an integer number (6504897).

Almost surely, 2^21682985 is an apocalyptic number.

It is an amenable number.

21682985 is a deficient number, since it is larger than the sum of its proper divisors (4336603).

21682985 is an equidigital number, since it uses as much as digits as its factorization.

21682985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4336602.

The product of its digits is 69120, while the sum is 41.

The square root of 21682985 is about 4656.4992215182. The cubic root of 21682985 is about 278.8515244821.

The spelling of 21682985 in words is "twenty-one million, six hundred eighty-two thousand, nine hundred eighty-five".