20391663 has 4 divisors (see below), whose sum is σ = 27188888. Its totient is φ = 13594440.

The previous prime is 20391661. The next prime is 20391671. The reversal of 20391663 is 36619302.

It is a happy number.

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

It is not a de Polignac number, because 20391663 - 2¹ = 20391661 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20391663.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20391661) 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, 3398608 + ... + 3398613.

It is an arithmetic number, because the mean of its divisors is an integer number (6797222).

Almost surely, 2^20391663 is an apocalyptic number.

20391663 is a deficient number, since it is larger than the sum of its proper divisors (6797225).

20391663 is an equidigital number, since it uses as much as digits as its factorization.

20391663 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6797224.

The product of its (nonzero) digits is 5832, while the sum is 30.

The square root of 20391663 is about 4515.7129005286. The cubic root of 20391663 is about 273.2022143608.

The spelling of 20391663 in words is "twenty million, three hundred ninety-one thousand, six hundred sixty-three".