21204224477 has 2 divisors, whose sum is σ = 21204224478. Its totient is φ = 21204224476.

The previous prime is 21204224453. The next prime is 21204224497. The reversal of 21204224477 is 77442240212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13250081881 + 7954142596 = 115109^2 + 89186^2 .

It is a cyclic number.

It is not a de Polignac number, because 21204224477 - 2⁶ = 21204224413 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21204224407) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10602112238 + 10602112239.

It is an arithmetic number, because the mean of its divisors is an integer number (10602112239).

Almost surely, 2^21204224477 is an apocalyptic number.

It is an amenable number.

21204224477 is a deficient number, since it is larger than the sum of its proper divisors (1).

21204224477 is an equidigital number, since it uses as much as digits as its factorization.

21204224477 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 50176, while the sum is 35.

Adding to 21204224477 its reverse (77442240212), we get a palindrome (98646464689).

The spelling of 21204224477 in words is "twenty-one billion, two hundred four million, two hundred twenty-four thousand, four hundred seventy-seven".