21280747 has 2 divisors, whose sum is σ = 21280748. Its totient is φ = 21280746.

The previous prime is 21280739. The next prime is 21280757. The reversal of 21280747 is 74708212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21280747 - 2³ = 21280739 is a prime.

It is not a weakly prime, because it can be changed into another prime (21280757) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10640373 + 10640374.

It is an arithmetic number, because the mean of its divisors is an integer number (10640374).

Almost surely, 2^21280747 is an apocalyptic number.

21280747 is a deficient number, since it is larger than the sum of its proper divisors (1).

21280747 is an equidigital number, since it uses as much as digits as its factorization.

21280747 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6272, while the sum is 31.

The square root of 21280747 is about 4613.1060035512. The cubic root of 21280747 is about 277.1164389462.

Adding to 21280747 its reverse (74708212), we get a palindrome (95988959).

The spelling of 21280747 in words is "twenty-one million, two hundred eighty thousand, seven hundred forty-seven".