21036991 has 2 divisors, whose sum is σ = 21036992. Its totient is φ = 21036990.

The previous prime is 21036959. The next prime is 21037013. The reversal of 21036991 is 19963012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21036991 - 2⁵ = 21036959 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21036791) 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, 10518495 + 10518496.

It is an arithmetic number, because the mean of its divisors is an integer number (10518496).

Almost surely, 2^21036991 is an apocalyptic number.

21036991 is a deficient number, since it is larger than the sum of its proper divisors (1).

21036991 is an equidigital number, since it uses as much as digits as its factorization.

21036991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2916, while the sum is 31.

The square root of 21036991 is about 4586.6099681573. The cubic root of 21036991 is about 276.0543152573.

The spelling of 21036991 in words is "twenty-one million, thirty-six thousand, nine hundred ninety-one".