20643187 has 2 divisors, whose sum is σ = 20643188. Its totient is φ = 20643186.

The previous prime is 20643173. The next prime is 20643191. The reversal of 20643187 is 78134602.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20643187 - 2¹¹ = 20641139 is a prime.

It is a super-2 number, since 2×20643187² = 852282339033938, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (20643107) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10321593 + 10321594.

It is an arithmetic number, because the mean of its divisors is an integer number (10321594).

Almost surely, 2^20643187 is an apocalyptic number.

20643187 is a deficient number, since it is larger than the sum of its proper divisors (1).

20643187 is an equidigital number, since it uses as much as digits as its factorization.

20643187 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8064, while the sum is 31.

The square root of 20643187 is about 4543.4774127314. The cubic root of 20643187 is about 274.3209117597.

Adding to 20643187 its reverse (78134602), we get a palindrome (98777789).

The spelling of 20643187 in words is "twenty million, six hundred forty-three thousand, one hundred eighty-seven".