21894890881 has 2 divisors, whose sum is σ = 21894890882. Its totient is φ = 21894890880.

The previous prime is 21894890879. The next prime is 21894890909. The reversal of 21894890881 is 18809849812.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13286020225 + 8608870656 = 115265^2 + 92784^2 .

It is a cyclic number.

It is not a de Polignac number, because 21894890881 - 2¹ = 21894890879 is a prime.

It is a super-2 number, since 2×21894890881² (a number of 21 digits) contains 22 as substring.

Together with 21894890879, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21894890081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10947445440 + 10947445441.

It is an arithmetic number, because the mean of its divisors is an integer number (10947445441).

Almost surely, 2^21894890881 is an apocalyptic number.

It is an amenable number.

21894890881 is a deficient number, since it is larger than the sum of its proper divisors (1).

21894890881 is an equidigital number, since it uses as much as digits as its factorization.

21894890881 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2654208, while the sum is 58.

The spelling of 21894890881 in words is "twenty-one billion, eight hundred ninety-four million, eight hundred ninety thousand, eight hundred eighty-one".