21168491 has 2 divisors, whose sum is σ = 21168492. Its totient is φ = 21168490.

The previous prime is 21168481. The next prime is 21168509. The reversal of 21168491 is 19486112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21168491 - 2¹⁰ = 21167467 is a prime.

It is a super-2 number, since 2×21168491² = 896210022434162, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21168461) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10584245 + 10584246.

It is an arithmetic number, because the mean of its divisors is an integer number (10584246).

Almost surely, 2^21168491 is an apocalyptic number.

21168491 is a deficient number, since it is larger than the sum of its proper divisors (1).

21168491 is an equidigital number, since it uses as much as digits as its factorization.

21168491 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3456, while the sum is 32.

The square root of 21168491 is about 4600.9228422133. The cubic root of 21168491 is about 276.6283163243.

The spelling of 21168491 in words is "twenty-one million, one hundred sixty-eight thousand, four hundred ninety-one".