20409187 has 4 divisors (see below), whose sum is σ = 20794320. Its totient is φ = 20024056.

The previous prime is 20409157. The next prime is 20409199. The reversal of 20409187 is 78190402.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20409187 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20409107) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 192487 + ... + 192592.

It is an arithmetic number, because the mean of its divisors is an integer number (5198580).

Almost surely, 2^20409187 is an apocalyptic number.

20409187 is a deficient number, since it is larger than the sum of its proper divisors (385133).

20409187 is an equidigital number, since it uses as much as digits as its factorization.

20409187 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 385132.

The product of its (nonzero) digits is 4032, while the sum is 31.

The square root of 20409187 is about 4517.6528197727. The cubic root of 20409187 is about 273.2804526228.

Adding to 20409187 its reverse (78190402), we get a palindrome (98599589).

The spelling of 20409187 in words is "twenty million, four hundred nine thousand, one hundred eighty-seven".