21191081 has 2 divisors, whose sum is σ = 21191082. Its totient is φ = 21191080.

The previous prime is 21191077. The next prime is 21191111. The reversal of 21191081 is 18019112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11833600 + 9357481 = 3440^2 + 3059^2 .

It is a cyclic number.

It is not a de Polignac number, because 21191081 - 2² = 21191077 is a prime.

It is a super-2 number, since 2×21191081² = 898123827897122, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21191041) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10595540 + 10595541.

It is an arithmetic number, because the mean of its divisors is an integer number (10595541).

Almost surely, 2^21191081 is an apocalyptic number.

It is an amenable number.

21191081 is a deficient number, since it is larger than the sum of its proper divisors (1).

21191081 is an equidigital number, since it uses as much as digits as its factorization.

21191081 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 144, while the sum is 23.

The square root of 21191081 is about 4603.3771298906. The cubic root of 21191081 is about 276.7266828397.

The spelling of 21191081 in words is "twenty-one million, one hundred ninety-one thousand, eighty-one".