20491571 has 2 divisors, whose sum is σ = 20491572. Its totient is φ = 20491570.

The previous prime is 20491567. The next prime is 20491591. The reversal of 20491571 is 17519402.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20491571 - 2² = 20491567 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (20491561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10245785 + 10245786.

It is an arithmetic number, because the mean of its divisors is an integer number (10245786).

Almost surely, 2^20491571 is an apocalyptic number.

20491571 is a deficient number, since it is larger than the sum of its proper divisors (1).

20491571 is an equidigital number, since it uses as much as digits as its factorization.

20491571 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2520, while the sum is 29.

The square root of 20491571 is about 4526.7616460335. The cubic root of 20491571 is about 273.6476681519.

The spelling of 20491571 in words is "twenty million, four hundred ninety-one thousand, five hundred seventy-one".