20749509 has 24 divisors (see below), whose sum is σ = 33755904. Its totient is φ = 12168000.

The previous prime is 20749507. The next prime is 20749511. The reversal of 20749509 is 90594702.

It is an interprime number because it is at equal distance from previous prime (20749507) and next prime (20749511).

It is not a de Polignac number, because 20749509 - 2¹ = 20749507 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20749507) 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 23 ways as a sum of consecutive naturals, for example, 312 + ... + 6449.

It is an arithmetic number, because the mean of its divisors is an integer number (1406496).

Almost surely, 2^20749509 is an apocalyptic number.

It is an amenable number.

20749509 is a deficient number, since it is larger than the sum of its proper divisors (13006395).

20749509 is a wasteful number, since it uses less digits than its factorization.

20749509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6809 (or 6806 counting only the distinct ones).

The product of its (nonzero) digits is 22680, while the sum is 36.

The square root of 20749509 is about 4555.1628950017. The cubic root of 20749509 is about 274.7910655422.

The spelling of 20749509 in words is "twenty million, seven hundred forty-nine thousand, five hundred nine".