20431591 has 2 divisors, whose sum is σ = 20431592. Its totient is φ = 20431590.

The previous prime is 20431577. The next prime is 20431627. The reversal of 20431591 is 19513402.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20431591 - 2¹³ = 20423399 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20431091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10215795 + 10215796.

It is an arithmetic number, because the mean of its divisors is an integer number (10215796).

Almost surely, 2^20431591 is an apocalyptic number.

20431591 is a deficient number, since it is larger than the sum of its proper divisors (1).

20431591 is an equidigital number, since it uses as much as digits as its factorization.

20431591 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1080, while the sum is 25.

The square root of 20431591 is about 4520.1317458676. The cubic root of 20431591 is about 273.3804131013.

Adding to 20431591 its reverse (19513402), we get a palindrome (39944993).

The spelling of 20431591 in words is "twenty million, four hundred thirty-one thousand, five hundred ninety-one".