20671509 has 4 divisors (see below), whose sum is σ = 27562016. Its totient is φ = 13781004.

The previous prime is 20671499. The next prime is 20671517. The reversal of 20671509 is 90517602.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 20671509 - 2⁵ = 20671477 is a prime.

It is a super-2 number, since 2×20671509² = 854622568674162, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20671529) 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, 3445249 + ... + 3445254.

It is an arithmetic number, because the mean of its divisors is an integer number (6890504).

Almost surely, 2^20671509 is an apocalyptic number.

It is an amenable number.

20671509 is a deficient number, since it is larger than the sum of its proper divisors (6890507).

20671509 is an equidigital number, since it uses as much as digits as its factorization.

20671509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6890506.

The product of its (nonzero) digits is 3780, while the sum is 30.

The square root of 20671509 is about 4546.5931201285. The cubic root of 20671509 is about 274.4463085223.

The spelling of 20671509 in words is "twenty million, six hundred seventy-one thousand, five hundred nine".