20891071 has 2 divisors, whose sum is σ = 20891072. Its totient is φ = 20891070.

The previous prime is 20891047. The next prime is 20891081. The reversal of 20891071 is 17019802.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20891071 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20891041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10445535 + 10445536.

It is an arithmetic number, because the mean of its divisors is an integer number (10445536).

Almost surely, 2^20891071 is an apocalyptic number.

20891071 is a deficient number, since it is larger than the sum of its proper divisors (1).

20891071 is an equidigital number, since it uses as much as digits as its factorization.

20891071 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1008, while the sum is 28.

The square root of 20891071 is about 4570.6751142473. The cubic root of 20891071 is about 275.4145637101.

It can be divided in two parts, 208910 and 71, that added together give a triangular number (208981 = T₆₄₆).

The spelling of 20891071 in words is "twenty million, eight hundred ninety-one thousand, seventy-one".