20391599 has 2 divisors, whose sum is σ = 20391600. Its totient is φ = 20391598.

The previous prime is 20391587. The next prime is 20391647. The reversal of 20391599 is 99519302.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20391599 - 2¹² = 20387503 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20393599) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10195799 + 10195800.

It is an arithmetic number, because the mean of its divisors is an integer number (10195800).

Almost surely, 2^20391599 is an apocalyptic number.

20391599 is a deficient number, since it is larger than the sum of its proper divisors (1).

20391599 is an equidigital number, since it uses as much as digits as its factorization.

20391599 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 21870, while the sum is 38.

The square root of 20391599 is about 4515.7058141557. The cubic root of 20391599 is about 273.2019285420.

The spelling of 20391599 in words is "twenty million, three hundred ninety-one thousand, five hundred ninety-nine".