21096991 has 2 divisors, whose sum is σ = 21096992. Its totient is φ = 21096990.

The previous prime is 21096979. The next prime is 21097009. The reversal of 21096991 is 19969012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21096991 - 2¹³ = 21088799 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21096991.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21096931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10548495 + 10548496.

It is an arithmetic number, because the mean of its divisors is an integer number (10548496).

Almost surely, 2^21096991 is an apocalyptic number.

21096991 is a deficient number, since it is larger than the sum of its proper divisors (1).

21096991 is an equidigital number, since it uses as much as digits as its factorization.

21096991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8748, while the sum is 37.

The square root of 21096991 is about 4593.1460895556. The cubic root of 21096991 is about 276.3165127205.

The spelling of 21096991 in words is "twenty-one million, ninety-six thousand, nine hundred ninety-one".