21215147 has 2 divisors, whose sum is σ = 21215148. Its totient is φ = 21215146.

The previous prime is 21215143. The next prime is 21215203. The reversal of 21215147 is 74151212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21215147 - 2² = 21215143 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21215141) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10607573 + 10607574.

It is an arithmetic number, because the mean of its divisors is an integer number (10607574).

Almost surely, 2^21215147 is an apocalyptic number.

21215147 is a deficient number, since it is larger than the sum of its proper divisors (1).

21215147 is an equidigital number, since it uses as much as digits as its factorization.

21215147 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 560, while the sum is 23.

The square root of 21215147 is about 4605.9903386785. The cubic root of 21215147 is about 276.8313996130.

Adding to 21215147 its reverse (74151212), we get a palindrome (95366359).

The spelling of 21215147 in words is "twenty-one million, two hundred fifteen thousand, one hundred forty-seven".