20639923 has 2 divisors, whose sum is σ = 20639924. Its totient is φ = 20639922.

The previous prime is 20639903. The next prime is 20639939. The reversal of 20639923 is 32993602.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20639923 - 2⁵ = 20639891 is a prime.

It is not a weakly prime, because it can be changed into another prime (20639903) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10319961 + 10319962.

It is an arithmetic number, because the mean of its divisors is an integer number (10319962).

Almost surely, 2^20639923 is an apocalyptic number.

20639923 is a deficient number, since it is larger than the sum of its proper divisors (1).

20639923 is an equidigital number, since it uses as much as digits as its factorization.

20639923 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 17496, while the sum is 34.

The square root of 20639923 is about 4543.1182022923. The cubic root of 20639923 is about 274.3064529029.

The spelling of 20639923 in words is "twenty million, six hundred thirty-nine thousand, nine hundred twenty-three".