20506387 has 4 divisors (see below), whose sum is σ = 22370616. Its totient is φ = 18642160.

The previous prime is 20506351. The next prime is 20506391. The reversal of 20506387 is 78360502.

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

It is a cyclic number.

It is not a de Polignac number, because 20506387 - 2¹⁹ = 19982099 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20506327) 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, 932098 + ... + 932119.

It is an arithmetic number, because the mean of its divisors is an integer number (5592654).

Almost surely, 2^20506387 is an apocalyptic number.

20506387 is a deficient number, since it is larger than the sum of its proper divisors (1864229).

20506387 is a wasteful number, since it uses less digits than its factorization.

20506387 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1864228.

The product of its (nonzero) digits is 10080, while the sum is 31.

The square root of 20506387 is about 4528.3978402963. The cubic root of 20506387 is about 273.7136039962.

Adding to 20506387 its reverse (78360502), we get a palindrome (98866889).

The spelling of 20506387 in words is "twenty million, five hundred six thousand, three hundred eighty-seven".