21861447221 has 2 divisors, whose sum is σ = 21861447222. Its totient is φ = 21861447220.

The previous prime is 21861447217. The next prime is 21861447239. The reversal of 21861447221 is 12274416812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19737159121 + 2124288100 = 140489^2 + 46090^2 .

It is a cyclic number.

It is not a de Polignac number, because 21861447221 - 2² = 21861447217 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21861447821) 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, 10930723610 + 10930723611.

It is an arithmetic number, because the mean of its divisors is an integer number (10930723611).

Almost surely, 2^21861447221 is an apocalyptic number.

It is an amenable number.

21861447221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21861447221 is an equidigital number, since it uses as much as digits as its factorization.

21861447221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 43008, while the sum is 38.

The spelling of 21861447221 in words is "twenty-one billion, eight hundred sixty-one million, four hundred forty-seven thousand, two hundred twenty-one".