21320447 has 2 divisors, whose sum is σ = 21320448. Its totient is φ = 21320446.

The previous prime is 21320407. The next prime is 21320479. The reversal of 21320447 is 74402312.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21320447 is a prime.

It is a super-2 number, since 2×21320447² = 909122920559618, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21320407) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10660223 + 10660224.

It is an arithmetic number, because the mean of its divisors is an integer number (10660224).

Almost surely, 2^21320447 is an apocalyptic number.

21320447 is a deficient number, since it is larger than the sum of its proper divisors (1).

21320447 is an equidigital number, since it uses as much as digits as its factorization.

21320447 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1344, while the sum is 23.

The square root of 21320447 is about 4617.4069562905. The cubic root of 21320447 is about 277.2886554644.

Adding to 21320447 its reverse (74402312), we get a palindrome (95722759).

The spelling of 21320447 in words is "twenty-one million, three hundred twenty thousand, four hundred forty-seven".