20681917 has 8 divisors (see below), whose sum is σ = 21261240. Its totient is φ = 20106240.

The previous prime is 20681893. The next prime is 20681933. The reversal of 20681917 is 71918602.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 799236 + 19882681 = 894^2 + 4459^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20681917 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20681957) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13759 + ... + 15187.

It is an arithmetic number, because the mean of its divisors is an integer number (2657655).

Almost surely, 2^20681917 is an apocalyptic number.

It is an amenable number.

20681917 is a deficient number, since it is larger than the sum of its proper divisors (579323).

20681917 is a wasteful number, since it uses less digits than its factorization.

20681917 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1823.

The product of its (nonzero) digits is 6048, while the sum is 34.

The square root of 20681917 is about 4547.7375693855. The cubic root of 20681917 is about 274.4923615690.

The spelling of 20681917 in words is "twenty million, six hundred eighty-one thousand, nine hundred seventeen".