20809749 has 8 divisors (see below), whose sum is σ = 27792832. Its totient is φ = 13849920.

The previous prime is 20809729. The next prime is 20809757. The reversal of 20809749 is 94790802.

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

It is not a de Polignac number, because 20809749 - 2⁸ = 20809493 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 (20809709) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3604 + ... + 7389.

It is an arithmetic number, because the mean of its divisors is an integer number (3474104).

Almost surely, 2^20809749 is an apocalyptic number.

It is an amenable number.

20809749 is a deficient number, since it is larger than the sum of its proper divisors (6983083).

20809749 is a wasteful number, since it uses less digits than its factorization.

20809749 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11627.

The product of its (nonzero) digits is 36288, while the sum is 39.

The square root of 20809749 is about 4561.7703800170. The cubic root of 20809749 is about 275.0567331986.

The spelling of 20809749 in words is "twenty million, eight hundred nine thousand, seven hundred forty-nine".