20891081 has 2 divisors, whose sum is σ = 20891082. Its totient is φ = 20891080.

The previous prime is 20891071. The next prime is 20891083. The reversal of 20891081 is 18019802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20620681 + 270400 = 4541^2 + 520^2 .

It is a cyclic number.

It is not a de Polignac number, because 20891081 - 2¹⁰ = 20890057 is a prime.

It is a super-2 number, since 2×20891081² = 872874530697122, which contains 22 as substring.

Together with 20891083, 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 (20891083) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10445540 + 10445541.

It is an arithmetic number, because the mean of its divisors is an integer number (10445541).

Almost surely, 2^20891081 is an apocalyptic number.

It is an amenable number.

20891081 is a deficient number, since it is larger than the sum of its proper divisors (1).

20891081 is an equidigital number, since it uses as much as digits as its factorization.

20891081 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1152, while the sum is 29.

The square root of 20891081 is about 4570.6762081775. The cubic root of 20891081 is about 275.4146076546.

The spelling of 20891081 in words is "twenty million, eight hundred ninety-one thousand, eighty-one".