21281278747 has 4 divisors (see below), whose sum is σ = 22206551760. Its totient is φ = 20356005736.

The previous prime is 21281278727. The next prime is 21281278807. The reversal of 21281278747 is 74787218212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21281278747 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21281278747.

It is not an unprimeable number, because it can be changed into a prime (21281278727) 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 in 3 ways as a sum of consecutive naturals, for example, 462636472 + ... + 462636517.

It is an arithmetic number, because the mean of its divisors is an integer number (5551637940).

Almost surely, 2^21281278747 is an apocalyptic number.

21281278747 is a deficient number, since it is larger than the sum of its proper divisors (925273013).

21281278747 is an equidigital number, since it uses as much as digits as its factorization.

21281278747 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 925273012.

The product of its digits is 702464, while the sum is 49.

The spelling of 21281278747 in words is "twenty-one billion, two hundred eighty-one million, two hundred seventy-eight thousand, seven hundred forty-seven".