21801939449 has 2 divisors, whose sum is σ = 21801939450. Its totient is φ = 21801939448.

The previous prime is 21801939433. The next prime is 21801939451. The reversal of 21801939449 is 94493910812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19869721600 + 1932217849 = 140960^2 + 43957^2 .

It is a cyclic number.

It is not a de Polignac number, because 21801939449 - 2⁴ = 21801939433 is a prime.

Together with 21801939451, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21801939397 and 21801939406.

It is not a weakly prime, because it can be changed into another prime (21801939469) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10900969724 + 10900969725.

It is an arithmetic number, because the mean of its divisors is an integer number (10900969725).

Almost surely, 2^21801939449 is an apocalyptic number.

It is an amenable number.

21801939449 is a deficient number, since it is larger than the sum of its proper divisors (1).

21801939449 is an equidigital number, since it uses as much as digits as its factorization.

21801939449 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 559872, while the sum is 50.

The spelling of 21801939449 in words is "twenty-one billion, eight hundred one million, nine hundred thirty-nine thousand, four hundred forty-nine".