20505623 has 2 divisors, whose sum is σ = 20505624.
Its totient is φ = 20505622.
The previous prime is 20505619. The next prime is 20505643. The reversal of 20505623 is 32650502.
It is a happy number.
It is a weak prime.
It is a cyclic number.
It is not a de Polignac number, because 20505623 - 22 = 20505619 is a prime.
It is a Sophie Germain prime.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (20505643) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10252811 + 10252812.
It is an arithmetic number, because the mean of its divisors is an integer number (10252812).
Almost surely, 220505623 is an apocalyptic number.
20505623 is a deficient number, since it is larger than the sum of its proper divisors (1).
20505623 is an equidigital number, since it uses as much as digits as its factorization.
20505623 is an evil number, because the sum of its binary digits is even.
The product of its (nonzero) digits is 1800, while the sum is 23.
The square root of 20505623 is about 4528.3134829647.
The cubic root of 20505623 is about 273.7102047335.
The spelling of 20505623 in words is "twenty million, five hundred five thousand, six hundred twenty-three".