21199490891 has 2 divisors, whose sum is σ = 21199490892. Its totient is φ = 21199490890.

The previous prime is 21199490887. The next prime is 21199490911. The reversal of 21199490891 is 19809499112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21199490891 - 2² = 21199490887 is a prime.

It is not a weakly prime, because it can be changed into another prime (21199490801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10599745445 + 10599745446.

It is an arithmetic number, because the mean of its divisors is an integer number (10599745446).

Almost surely, 2^21199490891 is an apocalyptic number.

21199490891 is a deficient number, since it is larger than the sum of its proper divisors (1).

21199490891 is an equidigital number, since it uses as much as digits as its factorization.

21199490891 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 419904, while the sum is 53.

The spelling of 21199490891 in words is "twenty-one billion, one hundred ninety-nine million, four hundred ninety thousand, eight hundred ninety-one".