21961948891 has 2 divisors, whose sum is σ = 21961948892. Its totient is φ = 21961948890.

The previous prime is 21961948873. The next prime is 21961948949. The reversal of 21961948891 is 19884916912.

It is an a-pointer prime, because the next prime (21961948949) can be obtained adding 21961948891 to its sum of digits (58).

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21961948891 - 2⁵ = 21961948859 is a prime.

It is a super-2 number, since 2×21961948891² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21961943891) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10980974445 + 10980974446.

It is an arithmetic number, because the mean of its divisors is an integer number (10980974446).

Almost surely, 2^21961948891 is an apocalyptic number.

21961948891 is a deficient number, since it is larger than the sum of its proper divisors (1).

21961948891 is an equidigital number, since it uses as much as digits as its factorization.

21961948891 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2239488, while the sum is 58.

The spelling of 21961948891 in words is "twenty-one billion, nine hundred sixty-one million, nine hundred forty-eight thousand, eight hundred ninety-one".