21504044251 has 2 divisors, whose sum is σ = 21504044252. Its totient is φ = 21504044250.

The previous prime is 21504044213. The next prime is 21504044269. The reversal of 21504044251 is 15244040512.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21504044251 is a prime.

It is not a weakly prime, because it can be changed into another prime (21504044201) 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, 10752022125 + 10752022126.

It is an arithmetic number, because the mean of its divisors is an integer number (10752022126).

Almost surely, 2^21504044251 is an apocalyptic number.

21504044251 is a deficient number, since it is larger than the sum of its proper divisors (1).

21504044251 is an equidigital number, since it uses as much as digits as its factorization.

21504044251 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6400, while the sum is 28.

Adding to 21504044251 its reverse (15244040512), we get a palindrome (36748084763).

The spelling of 21504044251 in words is "twenty-one billion, five hundred four million, forty-four thousand, two hundred fifty-one".