20423999 has 4 divisors (see below), whose sum is σ = 20433864. Its totient is φ = 20414136.

The previous prime is 20423989. The next prime is 20424043. The reversal of 20423999 is 99932402.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 99932402 = 2 ⋅49966201.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20423999 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20423929) 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, 497 + ... + 6410.

It is an arithmetic number, because the mean of its divisors is an integer number (5108466).

Almost surely, 2^20423999 is an apocalyptic number.

20423999 is a deficient number, since it is larger than the sum of its proper divisors (9865).

20423999 is an equidigital number, since it uses as much as digits as its factorization.

20423999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9864.

The product of its (nonzero) digits is 34992, while the sum is 38.

The square root of 20423999 is about 4519.2918693087. The cubic root of 20423999 is about 273.3465478772.

The spelling of 20423999 in words is "twenty million, four hundred twenty-three thousand, nine hundred ninety-nine".