21221047 has 2 divisors, whose sum is σ = 21221048. Its totient is φ = 21221046.

The previous prime is 21221033. The next prime is 21221051. The reversal of 21221047 is 74012212.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21221047 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21221077) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610523 + 10610524.

It is an arithmetic number, because the mean of its divisors is an integer number (10610524).

Almost surely, 2^21221047 is an apocalyptic number.

21221047 is a deficient number, since it is larger than the sum of its proper divisors (1).

21221047 is an equidigital number, since it uses as much as digits as its factorization.

21221047 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 224, while the sum is 19.

The square root of 21221047 is about 4606.6307644525. The cubic root of 21221047 is about 276.8570597993.

Adding to 21221047 its reverse (74012212), we get a palindrome (95233259).

The spelling of 21221047 in words is "twenty-one million, two hundred twenty-one thousand, forty-seven".