20931663 has 4 divisors (see below), whose sum is σ = 27908888. Its totient is φ = 13954440.

The previous prime is 20931629. The next prime is 20931667. The reversal of 20931663 is 36613902.

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 20931663 - 2⁹ = 20931151 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 20931663.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20931667) 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, 3488608 + ... + 3488613.

It is an arithmetic number, because the mean of its divisors is an integer number (6977222).

Almost surely, 2^20931663 is an apocalyptic number.

20931663 is a deficient number, since it is larger than the sum of its proper divisors (6977225).

20931663 is an equidigital number, since it uses as much as digits as its factorization.

20931663 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6977224.

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

The square root of 20931663 is about 4575.1134412165. The cubic root of 20931663 is about 275.5928279868.

The spelling of 20931663 in words is "twenty million, nine hundred thirty-one thousand, six hundred sixty-three".