20309491 has 2 divisors, whose sum is σ = 20309492. Its totient is φ = 20309490.

The previous prime is 20309489. The next prime is 20309501. The reversal of 20309491 is 19490302.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20309491 - 2¹ = 20309489 is a prime.

Together with 20309489, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (20309431) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10154745 + 10154746.

It is an arithmetic number, because the mean of its divisors is an integer number (10154746).

Almost surely, 2^20309491 is an apocalyptic number.

20309491 is a deficient number, since it is larger than the sum of its proper divisors (1).

20309491 is an equidigital number, since it uses as much as digits as its factorization.

20309491 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1944, while the sum is 28.

The square root of 20309491 is about 4506.6052633884. The cubic root of 20309491 is about 272.8347472746.

Adding to 20309491 its reverse (19490302), we get a palindrome (39799793).

The spelling of 20309491 in words is "twenty million, three hundred nine thousand, four hundred ninety-one".