21281147 has 4 divisors (see below), whose sum is σ = 21290976. Its totient is φ = 21271320.

The previous prime is 21281137. The next prime is 21281149. The reversal of 21281147 is 74118212.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21281147 - 2⁸ = 21280891 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21281149) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 83 + ... + 6524.

It is an arithmetic number, because the mean of its divisors is an integer number (5322744).

Almost surely, 2^21281147 is an apocalyptic number.

21281147 is a deficient number, since it is larger than the sum of its proper divisors (9829).

21281147 is an equidigital number, since it uses as much as digits as its factorization.

21281147 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9828.

The product of its digits is 896, while the sum is 26.

The square root of 21281147 is about 4613.1493580850. The cubic root of 21281147 is about 277.1181751929.

Adding to 21281147 its reverse (74118212), we get a palindrome (95399359).

The spelling of 21281147 in words is "twenty-one million, two hundred eighty-one thousand, one hundred forty-seven".