20431891 has 2 divisors, whose sum is σ = 20431892. Its totient is φ = 20431890.

The previous prime is 20431867. The next prime is 20431913. The reversal of 20431891 is 19813402.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20431891 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (20431811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10215945 + 10215946.

It is an arithmetic number, because the mean of its divisors is an integer number (10215946).

Almost surely, 2^20431891 is an apocalyptic number.

20431891 is a deficient number, since it is larger than the sum of its proper divisors (1).

20431891 is an equidigital number, since it uses as much as digits as its factorization.

20431891 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 20431891 is about 4520.1649306192. The cubic root of 20431891 is about 273.3817511228.

The spelling of 20431891 in words is "twenty million, four hundred thirty-one thousand, eight hundred ninety-one".