21644581451 has 2 divisors, whose sum is σ = 21644581452. Its totient is φ = 21644581450.

The previous prime is 21644581447. The next prime is 21644581471. The reversal of 21644581451 is 15418544612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21644581451 - 2² = 21644581447 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21644581399 and 21644581408.

It is not a weakly prime, because it can be changed into another prime (21644581471) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10822290725 + 10822290726.

It is an arithmetic number, because the mean of its divisors is an integer number (10822290726).

Almost surely, 2^21644581451 is an apocalyptic number.

21644581451 is a deficient number, since it is larger than the sum of its proper divisors (1).

21644581451 is an equidigital number, since it uses as much as digits as its factorization.

21644581451 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 153600, while the sum is 41.

The spelling of 21644581451 in words is "twenty-one billion, six hundred forty-four million, five hundred eighty-one thousand, four hundred fifty-one".