21280347 has 32 divisors (see below), whose sum is σ = 34709760. Its totient is φ = 12778560.

The previous prime is 21280327. The next prime is 21280349. The reversal of 21280347 is 74308212.

It is not a de Polignac number, because 21280347 - 2⁷ = 21280219 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a self number, because there is not a number n which added to its sum of digits gives 21280347.

It is not an unprimeable number, because it can be changed into a prime (21280349) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 40428 + ... + 40950.

It is an arithmetic number, because the mean of its divisors is an integer number (1084680).

Almost surely, 2^21280347 is an apocalyptic number.

21280347 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21280347 is a deficient number, since it is larger than the sum of its proper divisors (13429413).

21280347 is a wasteful number, since it uses less digits than its factorization.

21280347 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 680 (or 674 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 27.

The square root of 21280347 is about 4613.0626486099. The cubic root of 21280347 is about 277.1147026777.

Adding to 21280347 its reverse (74308212), we get a palindrome (95588559).

The spelling of 21280347 in words is "twenty-one million, two hundred eighty thousand, three hundred forty-seven".