21144155447 has 2 divisors, whose sum is σ = 21144155448. Its totient is φ = 21144155446.

The previous prime is 21144155419. The next prime is 21144155479. The reversal of 21144155447 is 74455144112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21144155447 - 2¹² = 21144151351 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21144155447.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21144155147) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10572077723 + 10572077724.

It is an arithmetic number, because the mean of its divisors is an integer number (10572077724).

Almost surely, 2^21144155447 is an apocalyptic number.

21144155447 is a deficient number, since it is larger than the sum of its proper divisors (1).

21144155447 is an equidigital number, since it uses as much as digits as its factorization.

21144155447 is an evil number, because the sum of its binary digits is even.

The product of its digits is 89600, while the sum is 38.

Adding to 21144155447 its reverse (74455144112), we get a palindrome (95599299559).

The spelling of 21144155447 in words is "twenty-one billion, one hundred forty-four million, one hundred fifty-five thousand, four hundred forty-seven".