21147291 has 24 divisors (see below), whose sum is σ = 34441680. Its totient is φ = 12814560.

The previous prime is 21147289. The next prime is 21147317. The reversal of 21147291 is 19274112.

It is not a de Polignac number, because 21147291 - 2¹ = 21147289 is a prime.

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

It is not an unprimeable number, because it can be changed into a prime (21147211) 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 23 ways as a sum of consecutive naturals, for example, 31 + ... + 6503.

It is an arithmetic number, because the mean of its divisors is an integer number (1435070).

Almost surely, 2^21147291 is an apocalyptic number.

21147291 is a deficient number, since it is larger than the sum of its proper divisors (13294389).

21147291 is a wasteful number, since it uses less digits than its factorization.

21147291 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6504 (or 6487 counting only the distinct ones).

The product of its digits is 1008, while the sum is 27.

The square root of 21147291 is about 4598.6183794701. The cubic root of 21147291 is about 276.5359387878.

The spelling of 21147291 in words is "twenty-one million, one hundred forty-seven thousand, two hundred ninety-one".